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The Rogerley Mine

Fluorite from the mines of the Weardale valley in Northern England graces collections the world over.  It is famous for its bright emerald green and vivid purple crystals, beautiful interpenetrate twins and, due to the presence of rare earth elements, its natural daylight fluorescence.  Some of the most perfect and vibrant coloured specimens have come from the Rogerley quarry and mine, located towards the eastern end of the Weardale valley.  A former limestone quarry, this fluorite deposit has been mined for specimens since 1972 and was the first commercial specimen mine in Britain.  In mid-2017 a new phase of development commenced to re-examine the mineralised flats associated with the original Sutcliffe vein.

LOCATION

The name Weardale is derived from the River Wear and the northern English name dale for a river valley.  The River Wear rises in the Pennine hills close to the village of Cowshill and flows due east through Weardale and the city of Durham, finally entering the North Sea at Sunderland.  Weardale is approximately 31 km (19 miles) in length, coursing between the villages of Cowshill and Tow Law.  Within its bounds lie many towns and villages with names evocative of so many superb fluorite localities, for example Ireshopeburn, Blackdene, St. John’s Chapel, Daddry Shield, Westgate, Eastgate, Stanhope and Frosterley.  The Rogerley mine is located just west of Frosterley (Figure 1), on the southern slope of Fatherley Hill and almost opposite to where Rogerley Hall once stood, from where the name originates.  Scenery typical of the Weardale valley is illustrated in Figure 2.

Figure 1: Location of Rogerley mine in Weardale, County Durham, England.

Figure 2: Landscape and scenery in upper Weardale, near the village of Ireshopeburn, June 2008.  UK Mining Ventures LLC photo.

 

HISTORY AND PEOPLE

Discovery of fluorite at Rogerley quarry

Records of mining in the Weardale area date back to the 12th Century, chiefly for iron and lead, but also zinc, copper, silver and barium.  Limestone was an important commodity as a flux in iron and steel making and in more recent times the vast fluorite deposits have been exploited for this same purpose.  Towards the east, the ore field overlaps the Durham coalfield, hence the historic growth of the iron and steel industries in this area, synonymous with smelting towns such as Consett.

The original Rogerley Quarry was operated during the mid-19th century for limestone, an essential resource in the late period of the Industrial Revolution as a flux for iron making in the nearby foundries of Tow Law and Consett.  Just when the quarry closed is uncertain, but it certainly remained derelict for many years.

During the 1960s and 70s, mineral collecting in Britain was becoming a popular interest and Weardale was a productive hunting ground because of its numerous mines and much sought-after specimens.  Inevitably, collectors found their way to the spoil heaps and quarry floor at Rogerley where attractive specimens of green fluorite were quickly unearthed.

The first documented mineral collector to find specimen grade fluorite in the Rogerley quarry was Raymond Blackburn around 1970.  He recognised that the source of these specimens as a small zone high on the quarry’s north face, but not being keen on heights, chose not to climb or descend to the required zone.  Raymond Blackburn sold some of the specimens to the well-known Kendal-based collectors Lindsay and Patricia Greenbank.

Armed with Raymond Blackburn’s description of the likely source in the quarry face, the Greenbanks first visited the site in 1971.  Existing specimens from their initial finds from the quarry floor show sharp cubic crystals to 20 mm of a mid-sea to peppermint green with cloudy white centres, associated with small, partly etched, octahedral and cuboctahedral galena crystals (Figure 3).  Together with friends and collecting partners Michael (Mick) and Brenda Sutcliffe, the face exposure was investigated using electron ladders lowered from the top of the quarry (Ref. 6).  Cavities were found in the face near the top of the Great Limestone, a major stratigraphic unit in this area.  Mineralisation occurred associated with a North-South trending vein and horizontal flats emanating from the vein, later named the Greenbank vein by Sir Kingsley Dunham, then Professor Emeritus of Geology at the University of Durham and director of the British Geological Survey.

Figure 3: Fluorite with corroded galena. The first specimen collected in Rogerley quarry by Patricia Greenbank in 1971, prior to commencement of mining operations.  5.2 x 4.5 x 4.3 cm.

Figure 3: Fluorite with corroded galena. The first specimen collected in Rogerley quarry by Patricia Greenbank in 1971, prior to commencement of mining operations.  5.2 x 4.5 x 4.3 cm. Crystal Classics photos.

Specimen Mining at Rogerley

Specimen mining began at Rogerley in 1972 and from this point on the mine has been in almost continuous operation for specimen recovery.  Table 1 summarises the specimen recovery operations of the Rogerley quarry and mine.

Table 1: Summary of Rogerley mine operating companies

Period

Operating Company & Summary of Operations

1972 to 1996

Cumbria Mining and Mineral Company (CMMC)

Lindsay and Patricia Greenbank with Michael and Brenda Sutcliffe.

The first specimen mining project ever undertaken in the British Isles.  Necessary leases to the mineral rights for the quarry were obtained from the land agents acting on behalf of the Church Commissioners of England whereas public access and trespass rights were negotiated with the then land owner.  The specimen recovery operation was run mainly on a “weekend only” basis for close to 25 years.

1999 to 2016

UK Mining Ventures LLC (UKMV, LLC)

A small team of American collectors and mineral dealers.

Full time Summer season specimen mining began in May 1999 and ran every subsequent year until 2016.  Almost all the mine development was made during this period, together with most of the, now famous, named fluorite pockets (see Table 5).

2017 onwards

UK Mining Ventures Limited (UKMV Ltd.)

Ian and Diana Bruce.

Start of new mine development to follow-up an extensive geological investigation including surface and underground geological mapping and a laser imaging survey of all existing mine workings. Development of the outcrop of the Sutcliffe Vein in the western face of Rogerley quarry commenced in summer 2017 with the discovery of a 6 x 10 m richly mineralised fluorite cavity.  This section, named the Diana Maria mine, is characterised by a substrate of iron stained colourless quartz crystals covered with colour-zoned purple and green cubic fluorite crystals.  The fluorite is commonly associated with druzy overgrowths of creamy-white aragonite.

Lindsay and Patricia Greenbank are well known British mineral collectors and dealers, based in Kendal, Cumbria, in the English Lake District.  During the 1960s the Greenbanks began buying specimens from miners at the Groverake and Blackdene mines in Weardale, a 1.5-hour drive from Kendal.  This was initially to enhance their own collection, but due to the prolific supply of top grade specimens, this led to them taking specimens to trade while on holiday in Europe, so marking the beginning of their move into commercial dealing.  Patricia had been Lindsay’s collecting partner and they were married in 1973 (Ref. 21).  The Lindsay Greenbank mineral collection was first documented in Michael “Mick” Cooper’s Classic Minerals of Northern England – The Lindsay Greenbank Collection (Ref. 2) limited to fifty copies, in 1996.  However, in 2010 the collection became known to the widespread mineral community when an expanded version of Copper’s book was published in the Mineralogical Record special issue dedicated to his Northern England collection (Ref. 20).

Michael “Mick” and Brenda Sutcliffe were mineral collectors also living in Kendal and had already become friends with Patricia and Lindsay.  Mick originally grew-up in Blyth, Northumberland, and became interested in Northern England minerals after moving to Kendal while still a young man.  In 1972, the Greenbanks and Sutcliffes jointly formed the Cumbria Mining and Mineral Company (CMMC) to recover mineral specimens form the known, but unworked veins at Rogerley quarry in County Durham.  In 1982, Lindsay and Mick together with business partners Peter Blezard and Anne Danson formed the New Coledale Mining Company, Ltd. to operate the Force Crag mine near Keswick in the English Lake District, finally closing in 1990 due to a major collapse and build-up of water.

In 1996 Lindsay became very ill (Ref. 6 & 21), so ending mining operations and in 1998 it was decided to sell the mine; at this point a 35-metre-long adit (Ref. 11).  The Rogerley project was bought by a small group of American collectors and dealers, under the consortium name UK Mining Ventures LLC, with operations commencing in the summer of 1999.

The initial work was to make ready the mine following many years of relative neglect and unauthorised entry by collectors to high-grade.  Due to the somewhat high rainfall in Northern England, the mine workings tend to be very wet and so clay is transported into the workings, thereby masking the walls and working faces.  Once this was removed using power washers, promising mineralised zones were quickly identified and so began an annual summer collecting season which was to run for eighteen years. 

The many significant finds are described later, but of note was a large find of some 1,800 specimens in summer 1999; beautiful coloured fluorites from the West Cross Cut in 2001 and 2003 that sold at the St. Marie-aux-Mines show and those specimens from the Jewel Box and Rat Hole pockets which sold at the 2007 Denver show (Ref. 11).  The most famous specimen recovered by UKMV LCC was that of the Weardale Giant in 2012 (Ref. 15).  This was shown at the 2013 Tucson Gem and Mineral Show, but was subsequently reduced in size to make many smaller specimens.

Following almost twenty years of frequent transatlantic crossings, busy schedules and increasing operational challenges the partners of UKMV LLC decided to sell on the mining rights to a new operator and so the current phase of mining began.   

Ian and Diana Bruce are internationally known mineral dealers having formed Crystal Classics Fine Minerals in 1993.  Ian grew-up in Devonshire (Ref. 16), becoming interested in minerals at an early age.  Between graduating from Cardiff University in Mining Geology and starting Crystal Classics Fine Minerals, he collected full time in Cornwall and then Australia for eighteen months.  Following its closure in 1998, he was pivotal in driving a specimen recovery project at the world famous Tsumeb mine in Namibia, forming the Tsumeb Specimen Mining (Pty) Ltd with Simon Brock and David Lloyd.  By 2001, Tsumeb was back in operation as a specimen mine, but for only a short while due to insurmountable technical problems.  The mineral Ianbruceite is named for him, whose type locality is on 44 level in the Tsumeb mine.  Ian’s wife Diana is from an old Saxony family of mineral collectors and dealers.  In 2017, they formed the company UK Mining Ventures Limited, to continue specimen mining at Rogerley (Figure 4). 

Figure 4: Rogerley mine portal in the upper Great Limestone, June 2017 with Ian Bruce (left), the present mine operator.  UK Mining Ventures Ltd. photo.

GEOLOGY AND MINERALISATION

Regional Geology

Weardale lies within the Alston block; a horst of Carboniferous sediments bounded by the Stublick and Ninety Fathom faults (north), the Pennine Fault (west) and the Stainmore Trough.  Underlying the area is the North Pennine Batholith, also termed the Weardale granite.  The granite batholith has five plutons, the Weardale pluton being the largest and whose buoyancy in the crust is sufficient to uplift and maintain the horst above the adjacent areas.  Past deformation produced a dense grid of normal faulting in the Carboniferous limestones, sandstones and shales (mudstones) and it is these that were later mineralised to create the Northern Pennine Orefield (NPO) (Ref. 2, 4, 13, 17 & 18).

The main stratigraphic unit at Rogerley is the Great Limestone, in which the quarry was developed for the extraction of limestone.  The Great Limestone is a Carboniferous bioclastic packstone of the Pendleian Substage (326 Ma) whose reference section is in the nearby Eastgate quarry and in this area, sit at the top of the Alston Formation (Ref. 2 & 4).  The limestone, rich in crinoid debris, brachiopods and corals, is thickly bedded with interbeds of shaly mudstone partings following bedding.

Regional Mineralisation

The origin of mineralisation in and adjacent to the Weardale district has long been the subject of discussion and research, and work in this field continues today (Ref. 2, 17).  The type and distribution of mineralisation is partly analogous to both Mississippi Valley Type (MVT) (Ref. 5, 7 & 12) and hydrothermal zonation like that in Cornwall and Devon (Ref. 17).

The similarities to concentrically zoned mineralisation in Cornwall gave rise to the theory of an underlying Carboniferous (Variscan) granite mass, as proposed by Dunham in the early 1960’s.  Following a detailed gravity survey which appeared to confirm this, the Rookhope Borehole was drilled in 1960-61 in which the Weardale granite was encountered at 390.5 metres.  Initially this was regarded as the source of the mineralising fluids, but dating proved the Weardale granite to be Devonian, predating the Carboniferous host rock by around 100 million years.  This, and a weathering surface capping the granite boss, disproved the granite as the metallogenic source.

The carbonate-hosted (limestone) lead and zinc mineralisation of the Weardale mines has many similarities to those of MVT deposits, particularly those of a high fluorine presence such as the Illinois–Kentucky ore fields in the USA.

Element Sources and Mineral Concentration

Current knowledge (Refs. 1, 2, 3 & 4) suggests the sources of metals and fluorine were from several different sources which included:

  • the Weardale granite (a fluorine-rich boss of the underlying North Pennine Batholith).
  • the Whin Sill (late Carboniferous intrusion, dated at 295 million years).
  • metal-rich brines expelled from ongoing dewatering and lithification of adjacent sedimentary basins.
  • metals dissolved from adjacent country rocks by the passage of flowing brine.  Most arenaceous sedimentary rocks have a degree of permeability because of interconnectivity between the pore space of the naturally cemented rock grains.

Fluid pumping and circulation of the metal-rich brines through the host rocks was provided by various mechanisms including:

  • convection above the “high-heat retaining” Weardale batholith.
  • heat from the, then, recently injected Whin Sill.
  • natural overpressure within adjacent sedimentary basins from dewatering and diagenesis.

Faulting and Hydrothermal Vein Deposits

Permeability within the intervening country rock allowed these warm, metal-rich, hydrothermal brines to penetrate the Weardale sedimentary system, thereby entering any high permeability faults and fractures which are naturally present in the area.  Faults and fractures typically pervade competent (hard) rocks because these must “give” to allow the necessary crustal movement that results from natural stress relief mechanisms, including tectonic movement.  Softer rocks (i.e. none-brittle) can deform under stress and so do not “snap” to form faults.

The orientation of the vein, in both dip and strike, was controlled by the regional faulting regime prior to mineralisation.  An extensional tectonic regime was present towards the end of the Carboniferous, apparent from the contemporaneous intrusion of the Whin Sill across much of NE England.  Extensional regimes give rise to normal faulting mechanisms that naturally form fault planes at about 30° to the vertical. 

Metasomatic Replacement and Flat-style Ore Emplacement

The Weardale and Alston mining areas of Northern England are famous for their “flats”, the term given by miners to the near-horizontal rich ore deposits which extend out from the veins to distances of up to 200 m and at any vertical depth in the veins that is favourable.

Outward migration of ore-bearing fluid from the original, highly permeable, fault systems occurs through at least three processes:

  1. lateral extensions of faults through mechanical breakage of the adjacent limestones, in the form of brecciation, fracture development and growth and anastomosing (criss-crossing) fracture swarms.
  2. natural permeability within the rock fabric; i.e. fluid flow between intergranular pore space.
  3. Infiltration into very low permeability rock, driven by gravity and capillary pressure.

Geology and Mineralisation at the Rogerley Mine

The structural geology and mineralisation at the Rogerley mine is a microcosm of that at the regional scale.  Beneath Fatherley Hill, west of Frosterley, a near-vertical mineralised vein forms the central mineralising conduit of the deposit, within the upper unit of the Great Limestone.

Mineralised veins form within active faults.  These contain rubblised (brecciated) zones of high porosity and permeability and allow vertical fluid flow between horizontal beds of much lower permeability.  Changes in temperature, pressure, flow rate and flow direction, together with chemical reactivity with fault wall rock and rubble, have resulted in the precipitation and growth of fluorite crystals.  The vuggy porosity provided within the brecciated fault zone provided the accommodation space in which crystals of fluorite and galena could fully develop; these are termed euhedral crystals and for which Rogerley mine is now famous for.  Other minerals present, but to a much lesser extent, are aragonite, calcite, hydrocerussite, quartz and smithsonite (Ref. 7, 18, 19 & 21).

Around the sub-vertical vein system, metasomatic, horizontal mineralisation (flats) extends laterally; subparallel to the limestone country rock bedding.  A good example of this process was observed in the West Cross Cut.  The limestone country rock shows extensive replacement by iron carbonate minerals (ankerite and siderite).  Since deposition, these have oxidised through exposure to oxygen-rich groundwater and form a heavily iron-stained gossan-like matrix over which the fluorite has crystallised.

Figure 5 is an idealised sketch to illustrate some of the structural and mineralisation processes present at Rogerley.  The diagram shows a mineralised normal fault in a currently active state, thereby acting as a fluid conduit.  In this case, the term active does not imply movement is still occurring on the fault, but that the horizontal stress orientation is favourable to fluid flow.  Other faults trending at around 90° to this would have remained “closed”, acting as permeability barriers.  Radial fractures emanating from the fault system penetrate the limestone parallel to bedding and so allow the mineralising fluids to extend horizontally through the country rock.  Other processes are noted in the diagram, such as permeability controls to fluid flow and colour distribution in fluorite.

Figure 5: Sketch illustrating ore emplacement in veins and by metasomatic replacement along bedding (flats) at the Rogerley mine

Minerals

A relatively small number of mineral species have been found in Rogerley quarry and mine and are listed in Table 2 together with their chemical composition.  It is apparent from Table 2 that there is also a limited number of elements present (C, Ca, F, Fe, H, Mg, O, Pb, S and Zn) and these reflect the chemistry of the host rocks (mainly carbonates) and transported metals and halide (Fe, Pb, Mg, Zn and F). 

Table 2: Minerals found at the Rogerley Quarry and Mine

Mineral Species

Chemical Formula

Word-formula

Ankerite

Ca(Fe, Mg)(CO3)2

Calcium iron magnesium carbonate

Aragonite

CaCO3

Calcium carbonate

Calcite

CaCO3

Calcium carbonate

Dolomite

CaMg(CO3)2

Calcium magnesium carbonate

Fluorite

CaF2

Calcium fluoride

Galena

PbS

Lead sulphide

Hydrocerussite

Pb3(CO3)2(OH)2

Lead carbonate

Quartz

SiO2

Silicon oxide

Siderite

FeCO3

Iron carbonate

Smithsonite

ZnCO3

Zinc carbonate

Differences between Hydrothermal Vein and Replacement Flat-style Mineralogy

From the collector’s perspective, it is interesting to note that hydrothermal veins often contain larger (up to 8 cm on edge), single, fluorite crystals (i.e. untwinned), often of a more opaque, deep purple colour (Fig. 6).  Green (Fig. 7) and yellow fluorite is also found in the veins, but to a lesser extent.  The fluorite usually occurs with cuboctahedral and octahedral crystals of corroded galena.  The matrix of vein specimens is hard, dense ironstone, following replacement by iron-rich solutions.  Extracting specimens from these structures is difficult due to the rock’s hardness and the pockets being generally smaller than those found in the replacement pockets.

Fluorite crystals recovered from the metasomatic flats are typically smaller (Fig. 8), various shades of emerald-green and frequently twinned on the octahedral {111} plane (Fig. 9).  These are the famous penetration twins, also termed interpenetrant twins, for which many Weardale mines are famous. 

   

Examples of fluorite from the Greenbank vein, illustrating a tendency for the development of larger, single (untwinned) crystals in the mineralised veins at Rogerley. Fig. 6 shows an 8 x 6 x 3 cm purple Fluorite with Quartz.

Fig. 7 is a 15 x 12 x 7 cm of green Fluorite with mottled white centres on limestone.  UK Mining Ventures LLC photos.

   

Figures 8 & 9: Examples of fluorite from the metasomatic flats, showing cubic crystals, typically smaller than those found in the veins and the common presence of interpenetrant twins. Fig. 8 is a green Fluorite with a partial coating of Quartz (11 x 8 x 2 cm) from the Corner Pocket, West Crosscut, mined in 2003.

 

Fig. 9 is a deep leaf-green Fluorite on ironstone (7 x 6 x 3 cm) from the Bluebird Pocket Zone, recovered in 2015.  UK Mining Ventures LLC photos.

The cause of vivid colour in fluorite at Rogerley and other Weardale localities is still not clearly understood.  However, through modern analytical techniques and observation of colour change in specimens, it is believed green results from structural defects in the fluorite lattice (Ref. 7).  In the 1980s and 90s, rare earth elements (REEs) were considered a major cause of colour in Weardale fluorite, but this is now largely discredited.  This is not the case for fluorescence in Weardale fluorite.

Fluorescence and REE Elements

Weardale fluorite is renowned for its bright bluish-white fluorescence (Ref. 6) in longwave ultraviolet (LWUV) and natural daylight.  The term fluorescence derives its name from fluorspar, the old name for fluorite.  In artificial LWUV, Rogerley fluorite emits a bright bluish-white fluorescence, similar to many other Weardale localities.  What makes Rogerley fluorite remarkable is its ability to intensely fluoresce in daylight, termed daylight fluorescence.  This phenomenon is observed in some other Weardale fluorites, primarily those from the Heights mine and Eastgate (Blue Circle Cement) quarry, but much less intense.  Best observed in diffuse daylight rather than direct, emerald-green fluorite crystals from Rogerley glow an intense violet-blue. A vein specimen of fluorite, one of the earliest collected from Rogerley quarry, is shown in Figure 10, photographed in artificial light (left) and in daylight (right) for comparison.

 

Figure 10: Fluorite with Galena; transparent, interpenetrant twinned emerald-green crystals to 2 cm. specimen 16.5 x 9.0 x 5.8 cm, from West string, Greenbank vein, Rogerley quarry, Frosterley.  Photographed in artificial light (left) and scattered daylight (right), in which the Fluorite displays a patchy blue-violet natural fluorescence, termed daylight fluorescence.  Collected in 1970 by Lindsay Greenbank and Mick Sutcliffe, ex. Greenbank Collection, No. LG55.  Crystal Classics photo.

 

Much of the fluorite from both the veins and the flats displays this intense daylight fluorescence which surpasses that of most other known fluorite localities, both Weardale and world-wide.  Figures 11 and 12 show the same specimen from the Rat Tail pocket, collected in 2010; Figure 11 is as found and in daylight and Figure 12 in artificial light after cleaning.

Fig.11, Fluorite with Galena on Quartz, 17 x 10 x 3 cm, collected from the Rat Tail Pocket in 2010.  The “as found” specimen shows rich blue-green daylight fluorescence and at this stage the galena crystals are still coated with iron-stained aragonite. 

Figure 12 is after cleaning and shows the true (non- non-fluorescing) emerald-green Fluorite colour.

UK Mining Ventures LLC photos.

The daylight fluorescence of some fluorite has a totally captivating due to incredulity that the colour can be so extreme and strong.  Examples of this are shown in the freshly cleaned specimens from the Bluebirds Pocket Zone (Figure 13) and the Blue Bell Pocket (Figure 14), photographed just outside the Rogerley mine portal. 

Examples of Rogerley mine fluorite with intense blue daylight fluorescence.  Figure 13 is an 8 x 6 x 4 cm plate of single and interpenetrant Fluorite crystals on ironstone collected in the Bluebirds Pocket Zone in 2013

The specimens in Figure 14 were collected on 8th June 2009 from the Blue Bell Pocket.  The overall length of the Estwing hammer is 30.5 cm.  UK Mining Ventures LLC photos.

The high rare earth element (REE) content of Weardale fluorite has been known for many decades and this is, most likely, the primary cause of its daylight and LWUV fluorescence.  Ixer (Ref. 6 & 10) describes the differences in REE content between early, high temperature, fluorite mineralisation in the Northern Pennine Orefield and that of the late stage, low temperature, as found at Rogerley.  The REEs present in the Weardale ore field are listed in Table 3.

Table 3: Rare Earth Elements (REEs) present at Weardale and Rogerley Quarry and Mine (summarised from analysis set out in Ref. 10).

Rare Earth Element

Symbol

Weardale Fluorite

Rogerley Fluorite

Cerium

Ce

Dysprosium

Dy

Erbium

Er

Europium

Eu

Gadolinium

Gd

Lanthanum

La

Neodymium

Nd

Praseodymium

Pr

Samarium

Sm

Ytterbium

Yb

Yttrium

Y

indicates relatively high wt% concentrations, all > 1% wt/wt of sample

indicates very low (>>1% wt/wt), below detection level or not present

Early phase fluorite, above the cupolas of the Weardale Granite batholith, contains REEs in the form of discrete mineral inclusions, as set out in Table 4.

Table 4: REE-containing minerals present in early stage, high temperature fluorite (summarised from analysis set out in Ref. 10).

Mineral Species

Chemical Formula

Remarks

Monazite-(Ce)

(CeLaNdPrY)P O4

High wt% of five REEs occurs in monazite

Synchysite-(Ce)

Ca(CeLaNd)(CO3)2F

Xenotime-(Y)

YPO4

Containing : Dy, Er, Yb, Gd, Sm, Ce, La, Pr & U

Analysis by direct-coupled plasma spectroscopy (Ref. 7) of Rogerley mine specimens shows elevated REE levels in all colours of fluorite (green, purple and yellow) from both hydrothermal veins and metasomatic flats.  Interestingly, whereas europium was previously considered to be the main activator, levels of this element are low at Rogerley.  REE enrichment is primarily by lanthanum (La), cerium (Ce) and yttrium (Y); other REEs identified in the Rogerley fluorite are neodymium (Nd), samarium (Sm), gadolinium (Gd), dysprosium (Dy) and erbium (Er) (Ref. 6 & 10).

Summary of Notable Specimen Finds at the Rogerley Quarry and Mine

Almost fifty years have now passed since the specimen potential of Rogerley quarry was first recognised.  During this period, lots of wonderful discoveries have been made and readers will be aware of the many references describing many of these scattered throughout the literature and the internet.  An attempt is made here to collate all such records of specimen finds, together with the specific mineralogical characteristics of individual veins and pockets.  The advantage of web-based articles such as this is that updates can be made at will, as new information comes to light.  Characterisation of the mineralogy of veins and pockets really needs to be done at the time of discovery, chiefly because of the very limited number of mineral species present in the mine and hence few significant differentiators.  This is especially true in the case of collectable specimens which manly comprise of cubic green fluorite, cuboctahedral galena; sucrosic quart coatings and occasional calcite.  Many zones within the veins and replacement flats do exhibit characteristic differences, but these are often subtle in terms of colour, morphology, texture, associations, matrix and fluorescence.

Some outstanding finds during Rogerley’s history include rare, blackberry-purple fluorite; other scarce purple and yellow fluorites associated with vein mineralisation; the Weardale Giant; pockets which exhibit exceptional daylight fluorescence and very rarely, fluorites covering Palaeozoic fossil corals such as Actinocyathus floriformis sp.  When prepared into thin section mounts, such corals display the most delicate of structures at the microscopic scale (Ref. 7), so giving a clear indication of the piecemeal metasomatic replacement process which took place during flat-style mineralisation.

Based on a detailed study of the literature, internet articles, specimen descriptions and personal accounts, Table 5 has been complied.  In addition to a summary of specimen finds and their mineralogy, it also provides a record of mine development, structural geology and noteworthy events.

Table 5: Summary of major discoveries at the Rogerley Quarry and Mine

The basis of this table is used with the kind permission of UK Mining Ventures, LLC. (Ref. 7, 8 & 9).  Other information is drawn from numerous sources, including details recorded on specimen labels and personal communication between the author and the mine owners, both former and current.  Figure references within Table 5 in green text refer to previous figures in this article.  Figure references within Table 5 in gold text follow-on in the section Mining and Mineral Gallery. The Gallery section follows the chronologic sequence of mining and specimen acquisition.

Period/Date

Zone/Vein/Pocket

Mineralogy & Comments

Limestone quarrying period

Mid-19th century

(actual operating period unknown)

Working limestone quarry

Opencast quarrying operation adjacent to, and north of the A689 Stanhope to Frosterley road.  Limestone production.  Minerals from the veins and flats were tipped in a waste dump.

Mineral Collectors period

Circa 1970-1972

Spoil heap of mineral-rich “waste” and strewn limestone blocks in the quarry

Collector Raymond Blackburn is attributed (Ref. 7 & 20) with discovering specimen grade fluorite and galena, most likely in the old dump.  Other collectors then got to know about the site and a period of specimen collecting from material strewn over the quarry floor commenced.

Cumbria Mining and Mineral Company (CMMC)

1972

Quarry floor and faces.  Many faces were inaccessible.

Figure 3

Lindsay and Patricia Greenbank begin collecting and evaluating the quarry and enlist collecting friends Michael “Mick” and Brenda Sutcliffe as partners in the Cumbria Mining and Mineral Company (CMMC).

1972 to 1975

High Flats Horizon (Greenbank vein)

10 m long quarry bench, 20 m above the quarry floor.

1976

Surface work (un-named Sutcliffe vein)

Good quality green and purple fluorite.  The, yet unnamed, Sutcliffe vein on the top bench of the disused quarry.

Late 1970’s

Greenbank vein

Figures 6 & 7

A cavity containing exceptional bright green fluorite was discovered near the surface directly below the previously cut bench level.  Vein named by Sir Kingsley Dunham in recognition of Lindsay and Patricia Greenbank.

1980 to 1995

Mainly the Greenbank vein and adjacent, but unnamed pockets

Figure 10

All the specimens mined over this period were from the adit being driven along the Greenbank vein and adjacent flats.  Specific pockets or exact localities within the mine are not documented, save for on the detailed labels usually accompanying the specimens (now in private collections).  For reasons unknown, some specimens over this period were incorrectly attributed to the Eastgate quarry, also known as the Blue Circle Cement quarry (Ref. 20).  Collation of data from old labels is currently ongoing.

1996

Final season of CMMC operations at Rogerley.  Closure was necessary due to Lindsay Greenbank suffering the onset of ill health.

UK Mining Ventures, LLC (UKMV)

1999 to 2000

Weasel pocket

(Greenbank vein)

Figure 15

The largest vein pocket discovered to date which produced several large clusters of untwinned purple fluorite crystals, some coated with white finely crystalline druzy quartz.  The fluorite crystals were opaque and slightly corroded, except around the edges (Ref. 6 & 11).

Pocket named for a stoat (mistaken for a weasel) who resided there.

1999 to 2001

Black Sheep pocket

Figures 16 & 17

Interconnected series of fluorite-lined solution cavities in the flats to the east of the vein.  Opened-up to a length of approximately 5 m, the wall rock surrounding these cavities was highly silicified.  Zoned crystals found with green edges and inner blue or yellow cores and phantoms.

Pocket named for a local ale popular with the mining crew.

2000

Sutcliffe vein

Figure 18

A previously unrecognized mineral vein in the Rogerley Quarry was named the Sutcliffe Vein in recognition of Mick’s contributions to the mining and specimen mineralogy of the area.

2001

Birthday pocket

After driving the new east adit through a highly brecciated zone, an area of flats to the northeast of the Black Sheep, now known as the “Birthday Pocket”, was encountered.  This area of flats produced some good, and often large plates covered with twinned green fluorite crystals, many

showing patches of incipient alteration. Pocket named for its discovery on one of the partners wife’s the birthday.

2001 to 2003

The Dipper pocket

Fairly-well brecciated, but only a small number of good-quality specimens recovered.  Pocket named because the mineralized flats appeared to dip into the floor of the adit.

21st June 2001

Mid-summer’s day

Solstice pocket

A cavity in one of the flats was discovered along the main adit, about 10 meters north of the original Black Sheep Pocket opening.  Specimens from this area, though not numerous, were of very high quality, showing good lustre or very little corrosion. Pocket named for discovery date.

2001

end of season

to summer 2003

West Cross Cut

Figures 19 & 20

Started opposite the Black Sheep Pocket to see if flats existed to the west of the main vein as well as to the east. After a couple of blasts, green fluorite specimens were found here and this has proven to be the most productive area of flats yet found in the mine.  The area around the West Crosscut has undergone extensive replacement by iron carbonates rather than silica.  These have oxidized creating a heavily iron stained gossan-like matrix for the fluorite in much of the area.

2001 to 2010

West Crosscut pocket zone

Extensive replacement by the iron carbonate minerals ankerite and siderite.  Pocket named for its location within the mine.

2003 to 2004

The Corner pocket

Figure 8

Not large, but produced some unique specimens for Rogerley.  Most of the fluorite crystals were small and a lightish-green colour, but had a late-stage coating of fine-grained sucrosic quartz.  Pocket named for its location at the northern edge of the West Crosscut zone.

2006

The Tube

While driving an exploratory crosscut eastward from the main adit, a long, narrow, tube-like pocket was found.  Much of the pocket was lined with massive galena, and several large, crudely formed cuboctahedral galena crystals were found.  Several fluorite clusters of an unusual pale green colour with internal purple layers associated with quartz were also recovered from this pocket.  Pocket named for its structure.

2006

The Dodgy Bugger pocket

Found on the southern area of the West Crosscut zone. Pocket named because most good specimens were on large, loose rocks in the roof, making collecting difficult and dangerous.

2007 to 2008

The Rat Hole pocket

Clusters of larger, untwinned fluorite crystals, often on a layer of white quartz. Galena, common elsewhere, was almost totally absent here.  This pocket was a long, narrow tube, lined with fluorite and produced hundreds of good-quality specimens.  Pocket named for its long narrow shape and confined space, allowing only one person to collect at a time.

2009 (August) &

2010 (June)

The Rat Tail pocket

Figures 11 & 12

Figure 21

Although smaller than the Rat Hole, the fluorite from this pocket was generally much more gemmy and lustrous, and of a deeper, more saturated colour. The Rat Tail Pocket was very near surface at the face of the quarry and by July 2010 it began to collapse and had to be back-filled for safety.  Pocket named as it was an extension of the Rat Hole Pocket.

2007 (mid-July)

to 2008

The Jewel Box pocket

Figure 22

Over the first several years a few interesting pockets were encountered along the main vein, but never anything that gave up much in the way of quality specimens.  In mid-July 2007, after mucking out the blast debris at the main face, a clay-filled pocket zone was discovered trending eastward from the vein. The pocket was mainly collapsed and brecciated, but produced some very fine specimens of flawless, deep green twinned fluorite crystals.

Pocket named for a few of the finest specimens yet found in the mine.

2008 (July/August & 2009 (June)

The Blue Bell pocket

Figure 14 & Figure 23

Many high-quality specimens; quite like the Jewel Box, but a little larger.  Pocket named after the favourite local pub, the Blue Bell Inn in St. Johns Chapel.

2009 (late July)

High pocket

A small pocket at the north end of The Jewel Box-Blue Bell Pocket Zone. Pocket named because a ladder was needed to collect it. A small pocket, but produced one of the top specimens yet found in the mine.

2010 (July)

The Purple pocket

A reasonably large pocket containing purple fluorite, found near the Crushed Zone flats.  Pocket named colour of contained fluorite.

2010

The Crushed Zone

While tunnelling north along the vein past the Blue Bell Pocket in August 2009, the mineralized flats shifted from the east to the west side of the vein.  A fault zone also parallels the west side of the vein in this area of the mine; movement along the fault causing much disruption to the flats, and very few undamaged specimens were recovered.  This zone contained fluorite of a similar character to that in the Blue Bell Pocket.  Pocket named for brecciated/deformation zone.

2011 to end of June 2013

Penny’s pocket zone

Figure 24

A heavily brecciated pocket, the fluorites being thickly coated with both soft and hard (calcified) clay (Ref. 14).  Fluorite crystals are typically between a few mm to about 4 cm on edge, most of which are twinned, with a medium to good lustre, are very gemmy and have the best daylight fluorescence to this find. Crystal faces exhibit growth hillocks. Untwinned crystals are quite rare and usually of poorer quality.  One specimen is of a replaced colonial corral over which fluorite crystals have grown.

Pocket named for Penny Williamson, a visiting Australian friend of the mining team and curator of Geology at the University of Wollongong.

2012 (July)

The Weardale Giant – found within the Penny’s pocket zone.

Figure 25

The largest fluorite specimen found to date, a specimen about 1 m wide and weighing around 300 kg (Ref. 9).  The limestone matrix is coated with many hundreds of deep green fluorite cubic crystals which all exhibit an intense deep ink-blue daylight fluorescence.  Occasional interpenetrant cubes to about 7 cm are scattered amongst the smaller crystals.

The specimen is named (because of its size) for one of three legendary Giants of Weardale.  These were brothers who worked as blacksmiths on local surrounding hilltops.

2013 to 2014

The Bluebirds pocket zone No. 1

Figures 9 & 13

Figures 26 & 27

Opposite to Penny’s pocket, a new exploratory crosscut driving eastward was developed to investigate for corresponding flats on the east side of the main vein. After about two weeks a totally new pocket zone that was encountered and named the Bluebirds pocket.  This immediately began producing and through July and August gave some of the best material found since the Jewel Box and Blue Bell pockets in 2008.

Pocket named by team member Ian Jones in recognition of Cardiff City (nicknamed The Bluebirds) Football Club’s promotion to the Premier League in 2013; the first time in its 144 years history.

2014 to 2015

The Bluebirds pocket zone No. 2

A continuation of the Bluebirds pocket zone as mining progressed east away from the vein.

2016

Mining operations wound-down and the mine closed due to ever demanding mining legislation on storage and control of explosives.  UKMV, LLC dissolved.

UK Mining Ventures Limited (UKMV Ltd.)

Summer 2017

Sutcliffe vein

(Diana Maria mine)

Development of the Sutcliffe Vein in the western face of Rogerley quarry.  Between 10 to 20 ft. (3 to 6 m) of overburden removed resulting in the discovery of a 6 x 10 m richly mineralised fluorite cavity.  Produced emerald-green and blackberry-purple cubic fluorite crystals to 6 cm on edge and exhibiting an intense daylight fluorescent purple.  The fluorites, often exhibiting rich colour zoning, are frequently found covering druzy beds of clear to milky-white quartz crystals.  This new working, approximately 125 m NNW of the Rogerley mine portal, is named the Diana Maria mine, for Ian Bruce’s wife.

MINING and MINERAL GALLERY

 

Figure 15: Quartz on purple Fluorite; 10 x 8 x 5 cm, Weasel Pocket, Greenbank Vein, 2000.
UK Mining Ventures LLC photo.

Figure 16: Byron Weege collecting in the Black Sheep Pocket, 17 June 1999.

Figure 17: Fluorite with octahedral Galena on Quartz, 5 x 5 x 3 cm, Black Sheep Pocket, 1999.
UK Mining Ventures LLC photo.

Figure 18: Colour zoned Fluorite with Galena, FOV 5 cm, Sutcliffe Vein.  Recovered by Lindsay Greenbank and Mick Sutcliffe, circa 1975.  UK Mining Ventures LLC photo.

Figure 19: Fluorite exposed in the West Crosscut Pocket Zone, 30th May 2004.  UK Mining Ventures LLC photo.

Figure 20: Fluorite on ironstone, 25 x 10 x 5 cm, West Crosscut, 2002. UK Mining Ventures LLC photo.

Figure 21: Interior of the Rat Tail Pocket, 14th August 2009.  UK Mining Ventures LLC photo.

Figure 22: Fluorite on limestone, 15 x 13 x 5 cm, Jewel Box Pocket, 2007.  UK Mining Ventures LLC photo.

Figure 23: Fluorite on ironstone, 8 x 7 x 5 cm, Blue Bell Pocket, 2009.  UK Mining Ventures LLC photo.

Figure 24: Fluorite on ironstone, 8 x 6 x 4 cm, Penny’s Pocket, 2012.  UK Mining Ventures LLC photo.

Figure 25: The Weardale Giant, prior to cleaning, outside Rogerley mine, 19th July 2012.  Pictured alongside are Jurgen Margraf (left) and Robert Brandstetter.  UK Mining Ventures LLC photo.

Figure 26: Bluebirds Pocket, 14th August 2013.  UK Mining Ventures LLC photo.

Figure 27: Corroded cuboctahedral Galena with Fluorite, 5 x 4 x 3 cm, Bluebirds Pocket Zone.  UK Mining Ventures LLC photo.

Figure 28: UK Mining Ventures display of Rogerley Mine Fluorite, Tucson Gem & Mineral Show, 2015.  Philip Taylor photo.

ACKNOWLEDGMENTS

Grateful acknowledgment is given to the directors of former UK Mining Ventures, LLC, for their generosity in so readily suppling information and many of the photographs used in this article.  Ian and Diana Bruce of Crystal Classics Fine Minerals Limited and UK Mining Ventures Ltd. are thanked for access to Rogerley specimens; the photo used in Figure 4 and information concerning the current specimen recovery operation.  Due thanks also to Steven Rust of Crystal Classics for discussions on his field observations throughout his many visits to the Weardale area.

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