In 2017 ownership of the Rogerley mining operation changed to that of Ian and Diana Bruce, under the name UK Mining Ventures Ltd. While initial upgrading of the Rogerley mine was in progress, opencast surface mining commenced around the outcrop of the old Sutcliffe Vein in Rogerley Quarry. This had only been very briefly worked by Lindsay Greenbank and Michael Sutcliffe back in the 1970’s and this new operation was named the Diana Maria mine (after Diana Bruce) and this, along with Rogerley mine, is now operated throughout the entire year.
Initial preparatory work at the outcrop exposed high quality, classic green Fluorite specimens which gave great encouragement to pursue the vein underground. Since the summer of 2017 the mine has been developed underground and is producing stunning world class specimens that include emerald-green, purple, some yellow Fluorites, multi-coloured zoned crystals, amazing twinned crystals and, rarely, crystals containing fluid inclusions in the form of movable bubbles. Occasionally the Fluorite mineralisation is associated with snowy-white Calcite which contrasts superbly with the colourful cubic fluorite crystals. Once again, the Fluorite emits amazing fluorescence in natural daylight.
Spectacular Fluorite specimens continue to be discovered as the Diana Marine mine and some of the most gemmy crystals are being used to produce beautiful faceted stones for both the collector and as jewellery.
Since the Greenbanks and Sutcliffes began exploring the long abandoned Rogerley quarry in the early 1970s, two mineralised veins have been known to crop out in the quarry face; the Greenbank vein and the Sutcliffe vein. These two veins strike normal (at 90°) to one another and all mining operations up to early 2017 concentrated on the Greenbank vein, exploited by Rogerley mine. Some collecting had been done from the exposure of the Sutcliffe vein by Lindsay Greenbank and Mick Sutcliffe using ropes and abseiling equipment, but this was difficult and so abandoned in favour of the Greenbank vein and the development of Rogerley mine.
The Diana Maria mine originates from the summer months of 2017, shortly after the Rogerley specimen recovery project changed ownership from its North American partners (UK Mining Ventures LLC) to Ian and Diana Bruce under the name UK Mining Ventures Ltd. (UKMV Ltd).
Before mining operations in Rogerley mine could resume, an extensive refurbishment programme had to be conducted to ensure full compliance with HM Inspectorate of Mines standards. While this work was underway the specimen recovery team turned their attention to the Sutcliffe vein, some 400m west of the Rogerley mine main portal, cropping out on the face of Rogerley quarry. Shortly after beginning removal of overburden adjacent to the Sutcliffe vein, richly mineralised collapsed flats were exhumed, hosting a stunning variety of Fluorite specimens and exhibiting wonderful daylight fluorescence. This was the first confirmed indication that exploitation of the Sutcliffe vein was a viable proposition and the operation to mine the vein was named the Diana Maria mine, for Ian's wife (Fig. 1)
This subsurface plan of Diana Maria mine shows every major named mineralised pocket discovered. It shows the spatial distribution and varied mineralogy along the Greenbank Vein, so allowing collectors to pinpoint where their specimens originated.
This section is a repository for photographs and associated information taken since mining operations began in 2017, documenting mineral discoveries and development of the Diana Maria mine.
Three photographic archives contain a wide selection of photos which will be added to whenever new material is appears.
In early summer 2017, UKMV Ltd. commissioned a consultancy to undertake geological mapping and modelling of the Rogerley quarry and adjacent area and it was during this investigation a third vein was discovered; the River Catcher vein. This is close to, and runs parallel with, the Sutcliffe vein. The three mineralised veins are plotted on the map shown in Figure 2 and a view of the Sutcliffe vein in relation to the River Catcher vein is provided in Figure 3.
The mineralised veins have formed within open faults within the upper unit of the Great Limestone. Figure 3 is an idealised sketch to illustrate some of the structural and mineralisation processes present in the Sutcliffe vein at Diana Maria mine.
The diagram shows a steeply dipping mineralised normal fault in a currently active state, thereby acting as a fluid conduit. In such a 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, so allowing 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.
These contain rubblised (brecciated) zones of high porosity and permeability and allow vertical fluid flow between horizontal beds of much lower permeability.
Since mining began at Diana Maria, the Sutcliffe vein is observed to be a more densely mineralised shear structure traversing old karst horizons. It has two distinct zones, divided by the vein/shear zone which runs East- West. To the right of the mine are the Southern Flats and to the left, the Northern Flats. The sheared and brecciated texture of the veins can be clearly seen in the River Catcher vein, Figure 4.
In the period to early summer 2019, the Northern Flats tended to produce purple fluorite, and this is where the Purple Haze pocket was found. The Northern Flats are more heavily mineralised than the Southern and tend to contain larger fluorite crystals, although often of an inferior quality to the Southern. Bucking this trend were the specimens from the Purple Haze pocket, many of which are magnificent. Examples of some of these can be seen in the Photographic Archive areas of this website. The Southern Flats tend to produce green fluorite, but in many shades and colour zoning habits. Examples include the beautiful gemmy crystals found in the Queen of Green and November Gem pockets. A marked mineralogical variation was that of the Green Sugar pocket, where Fluorite occurred with pervasive druses of 1 to 3 mm colourless Quartz crystals, often tinged green because of the Fluorite beneath.
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. These and other controls affecting Mineralisation in Veins, Replacement Flats and at Vein and Flat Intersections are set out in Table 2. 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 Diana Maria mine is now famous for. Other minerals present, but to a much lesser extent, are aragonite, calcite, hydrocerussite, quartz and smithsonite (Fisher and Greenbank, 2003; Symes and Young, 2008; Tindle, 2008 & Wilson, 2017).
|Chemical controls||Physical controls|
|Fluid composition||Pressure & pressure gradients|
|Fluid source: single or multiple||Localised convection cells|
|Dissolved gas: type and volume||Fault and orebody architecture|
|Acidity-alkalinity, pH||Fracture geometry|
|Oxidation potential, Eh||In situ stresses|
|Rock-chemistry properties||Rock strength|
|Wallrock composition||Rock permeability & porosity|
|Wallrock reactivity: fluid transport path||Flow rate, flow path & duration|
|Wallrock reactivity: depositional zone||Hydraulic connectivity|
A common observation throughout the mines of Weardale is hydrothermal veins often contain larger, single, fluorite crystals (i.e. untwinned) and often of a more opaque, deep purple colour and to a lesser extent, green and yellow.
Around the sub-vertical vein system, metasomatic, horizontal mineralisation (flats) extends laterally; subparallel to the limestone country rock bedding. 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.
Mapping strike direction and geological modelling (Figure 5) of the veins indicate their intersection to the north of both current underground mining operations. Figure 5 also indicates the strike and dip of the Greenbank sub-parallel vein which bifurcates from the primary Greenbank vein very close to the Rogerley mine portal.
Research into controls on ore localization commonly indicate increased complexity in the mineralogy where veins intersect. The differences between hydrothermal vein and replacement flat-style mineralogy are controlled by many factors and can be summarised primarily into chemical and physical controls, as set out below. Such controls will also dictate any differences in vein and flat mineralogy around the where the veins will intersect.
This is due to any differences in chemistry and physical properties in the mineralising fluids (metal and fluorine-rich brines in the case of the Rogerley veins); orebody architecture and physical differences in localised temperature, pressure and fault genesis. Because the near-vertical veins acted as fluid conduits to the formation metasomatic flat-stale mineralisation, so near to the intersection of the veins the flats themselves may well contain new mineral species to the area and new Fluorite colours and zoning.
The cause of vivid colour in fluorite at Diana Maria 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 (Fisher and Greenbank, 2003). 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. However, fluorescence in Weardale fluorite is attributed to REEs.
A relatively small number of mineral species have been found in the Diana Maria mine, typical of all mines along the Weardale valley. These 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, Cd, F, Fe, H, O, Pb, S, Si and Zn) and these reflect the chemistry of the host rocks (mainly carbonates) and transported metals and halide (Cd, Fe, Pb, Mg, Zn and F).
The cadmium sulphide polymorphs Greenockite and Hawleyite are included in Table 2 following the discovery of small powdery patches on some specimens in 2019. Currently recorded as greenockite, analysis has yet to confirm if it is the CdS polymorph, hawleyite. Collectors will be familiar with these two species from many of the mines and quarries in Derbyshire and know how difficult it is to distinguish between them. As more information from specimens from the Diana Maria mine becomes available, this note will be updated.
|Mineral Species||Chemical Formula||Word-formula|
|Greenockite / Hawleyite||CdS||Cadmium sulphide|
|Sphalerite||(Zn, Fe)S||Zinc sulphide|
Since specimen recovery began in the summer of 2017, many collectors have built fine suites of Fluorite portraying the varying aesthetics of the different pockets and zones within the Diana Maria mine. Two checklist tables follow:
The first table summarises the Diana Maria mineralised pockets; their discovery date, pocket name and origin of the name.
The second table is an expansion of the former, containing more detailed information suitable to the advanced collector. Any notable specimens finds are also recorded in this checklist.
|Period/Date||Origin of Pocket Name|
|Summer 2017||Graeber Jones pocket||For Charles Calvert "Cal" Graeber, Jr. and Ian Jones, British collector.|
|Summer 2017||Snowstorm pocket||For the drusy coating of snow-white Aragonite over the Fluorite crystals.|
|Summer 2017||Pavel's pocket||For Pavel Škácha, discoverer of the pocket.|
|Autumn 2017||Emerald Peaks pocket||For the Fluorite's colour and crystal habit in this zone.|
|Autumn 2017||Green Hill pocket||For the grassy green slopes of Fatherley Hill, on the side of which the Diana Maria mine is situated.|
|January 2018||Queen of Green pocket||For the stunning colour, gemminess and perfection of the Fluorite crystals lining this magnificent pocket.|
|Autumn 2018||Purple Haze pocket||For the smoky, very dark, almost black, purple Fluorite crystals, which appear a purple-coal black against the drusy snow-white Calcite coating.|
|Autumn 2018||Galena pocket||For the proliferation of well-crystallised Galena amongst the Fluorite.|
|November 2018||November Gem pocket||For the gem-quality Fluorite single and twin crystals and its month of discovery.|
|December 2018||Frosterley pocket||For the nearby village of Frosterley, first recorded as Forsterlegh in 1239, meaning 'the forester's clearing'.|
|February 2019||Green Sugar pocket||For the green-sucrosic appearance and texture of gemmy, colourless Quartz crystals overlaying green Fluorite.|
|May 2019||Papa pocket||For Diana Maria Bruce's father and German mineral dealer, Peter Schlegel.|
|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.|
|Cumbria Mining and Mineral Company (CMMC)|
|1976||Surface work (un-named Sutcliffe vein)||Lindsay and Patricia Greenbank with Mick and Brenda Sutcliffe discovered good quality green and purple fluorite in the, yet, unnamed Sutcliffe vein on the top bench of the disused quarry.|
|UK Mining Ventures, LLC (UKMV)|
|2000||Sutcliffe vein||UK Mining Ventures, LLC was run by the partnership of Cal and Kerith Graeber and Jessie and Joan Fisher. This previously unrecognized mineral vein in the Rogerley Quarry was named the Sutcliffe Vein in recognition of Mick's contributions to mining and fluorite specimen recovery in this area. The vein was not exploited until the operation was bought by Ian and Diana Bruce in 2017.|
|UK Mining Ventures Limited (UKMV Ltd.)|
|Diana Maria Opencast operations|
|Summer 2017||Sutcliffe vein||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 10m 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 drusy beds of clear to milky-white quartz crystals. This working is approximately 125 m NNW of the Rogerley mine portal. Named the Diana Maria mine in honour of Diana Maria Bruce; joint Director of the mine and Ian Bruce's wife.|
|Summer 2017||Graeber Jones pocket||The Graeber Jones Pocket was the first pocket discovered at the Diana Maria mine during June 2017. Initially it contained green, interpenetrant twinned fluorite crystals usually growing on equant, stubby quartz crystals, milky in appearance and tinged slightly yellow due to iron. The outer faces of the fluorite crystals tend to be a gemmy sea-green, with many of the centres slightly cloudy, in paler, mossy shades of green. This small zone quickly gave way to beautiful deep leaf-green to emerald-green twinned fluorites, often with distinct colour zoning. Zoned crystals often have a gemmy intense blackberry-purple centre surrounded with gemmy green faces. It is observed that these fluorites always grow on stubby quartz crystals, often of stalactitic form. Named for Charles Clavert "Cal" Graeber Jr., well-respected USA collector/dealer and one of the previous owners of Rogerley mine, and for British collector/dealer Ian Jones.|
|Summer 2017||Snowstorm pocket||The evocatively named Snowstorm Pocket occurred at the contact between the Sutcliffe vein and mineralised flat. This contained gemmy green fluorite twins coated with snow-white aragonite. The fluorite occurs mainly as green gemmy twins on quartz overcoated with snow-white aragonite. Occasionally, crystals can be a grassy to sea-green and, rarely, a purplish-green. Named for the drusy coating of snow-white Aragonite over the Fluorite crystals.|
|Summer 2017||Pavel's pocket||Pocket occurred on the south side of the Sutcliffe vein in a very hard jasperised limestone. The deep purplish-green fluorite is often prettily crazed with snowy-white centres and are typically directionally coated in drusy snow-white aragonite with one or two fluorite faces still visible. A frequent feature of this pocket is that of a larger gemmy purple twin emerging from the matrix. This observation of intense purple fluorite from the vein corroborates in-situ observations at the Greenbank vein. In daylight, the fluorite fluoresces an intense blackberry-purple. Named for Pavel Škácha, discoverer of the pocket.|
|Autumn 2017||Emerald Peaks pocket||The Emerald Peaks Pocket is characterised by small green untwinned fluorite crystals coating an ironstone matrix, over which much larger, gemmy emerald-green twinned crystals grow. Specimens show remarkable artificial UV and daylight fluorescence. Named for the Fluorite's colour and crystal habit in this zone.|
|Autumn 2017||Green Hill pocket||The Green Hill Pocket fluorites are most distinct with large intergrown single crystals, sometimes on a quartz matrix. The fluorites have beautiful gemmy corners with frosted and crazed green-mossy interiors, making spectacular combination. In daylight, the corners fluoresce intense blackberry-purple while their centres remain translucent, leaf-green mossy interiors, giving a stunning contrast. Named for the grassy green slopes of Fatherley Hill, on the side of which the Diana Maria mine is situated.|
|Diana Maria Underground operations|
|January 2018||Queen of Green pocket||To be described.
Named for the stunning colour, gemminess and perfection of the Fluorite crystals lining this magnificent pocket.
|Autumn 2018||Purple Haze pocket||To be described.
Named for the smoky, very dark, almost black, purple Fluorite crystals, which appear a purple-coal black against the drusy snow-white Calcite coating.
|Autumn 2018||Galena pocket||To be described.
Named for the proliferation of well-crystallised Galena amongst the Fluorite.
|November 2018||November Gem pocket||Typical of the November Gem pocket are 1 cm + cubic crystals of gemmy, mossy emerald-green fluorite. The crystals which are not gemmy are often shades of moss-green with cream to pale creamy-green crazed centres. When crazed, the faces are typically crazed also, but with gemmy corners reminiscent of the Green Hill pocket (2017). Fluorite crystals are both single and twinned and the larger crystals exhibit magnificent deep mauve-blue daylight fluorescence. The gemmy cubes typically measure from 0.7 to 1.4 cm and are occasionally distorted. The Fluorite is often coated with creamy-white Calcite either as undulating botryoidal coatings or delicate platy rosettes to 4 mm across. The largest fluorite crystal is a 2.6 x 2.0 x 1.8 cm cube. Named for the gem-quality Fluorite single and twin crystals and its month of discovery.|
|December 2018||Frosterley pocket||To be described.
Named for the nearby village of Frosterley, first recorded as Frosterley in 1239, meaning 'the forester's clearing'.
|February 2019||Green Sugar pocket||The Green Sugar fluorites range between candy-peppermint-green; emerald-sea-green, odd crystals showing internal yellow reflections to a beautiful deep leafy-emerald green. Cubes are typically about 6-8 cm and up to 1.5 cm on edge. The Fluorite is always associated with Quartz, and sometimes Galena and Calcite. The matrix is ironstone. Sucrosic 1-2 mm Quartz crystals richly coat many of the fluorite crystals. The quartz is colourless to light smoky brown and tan. Black galena crystals occur to 4 mm and form as modified cubes and octahedral crystals with flattened apexes. Snowy-white calcite may surround, and part cover the Fluorite crystals, some as small (5 mm) lenticular saucer-like crystals. Named for the green-sucrosic appearance and texture of gemmy, colourless Quartz crystals overlaying green Fluorite.|
|May 2019||Papa pocket||Named for Diana Maria Bruce's father and German mineral collector/dealer, Peter Schlegel.|
|June 2019||Why-Aye pocket||For the exclamation in local dialect “Wey-Aye”, pronounced “Why-Aye” meaning “Well Yes, of course!”.|
|Late Jun 2019||Gushing Water pocket||For the large flow rate of water issuing from this pocket. The pocket is connected to a high permeability fracture within the Great Limestone.|
|July 2019||4th July pocket||For its discovery on this date in 2019.|
|Mid-July 2019||Northern Flats pocket||For a cavity in the Northern Flats of the Sutcliffe vein, too small to be named as a pocket and with only a few specimens extracted.|
|Autumn 2019||Autumn pocket||For the season it was discovered and the rich golden-tan Quartz crystals.|
|Late Autumn 2019||Heavy Metal pocket||For the heavy nature of these specimens caused by the Galena content and the requirement to leave attached the enclosing brecciated matrix.|
|April 2020||Bypass pocket||For an unplanned small drive required in the Heavy Metal South Zone to bypass bad roof conditions encountered in the limestone overburden.|
|May 2020||Truffle Pig pocket||For how the miners discovered and recovered these large Fluorite crystals, on their hands and knees, reminiscent of truffling pigs!|
|Early September 2020||Milky Way pocket||For our galaxy, The Milky Way, and the night sky-black Fluorite crystals speckled by star-like bursts of white Fluorite. Discovered by Tom Costes.|
|June 2021||Hidden Forest pocket||For its stunning shades of forest green Fluorite, totally hidden by a thick coating of brown Calcite and only revealed once the Calcite is removed.|
|December 2021||Naughty Gnome pocket||For its brooding dark green, making the crystal-lined pocket a fitting lair for mischievous subterranean creatures like goblins, elves and gnomes!|
Opencast mining operations commenced at Diana Maria in summer 2017. A track-mounted front hoe excavator was used to scrap back the overburden, soil and rock debris surrounding the outcrop of the Sutcliffe vein. Working down from the top of the quarry face, the excavation gradually opened-up an accessible working area around the vein, some eight to twelve metres below the top of the quarry face. Once down to this level, excavation of the site quickly revealed a complexity of large collapsed flat-style mineralised pockets following the Sutcliffe vein along its northern and southern flanks. A cross section of the Northern Flats at Diana Maria in shown in Figure 5, seen here in 2017. The section shows rich fluorite mineralisation lining a large mud, clay and rubble filled cavity. Other examples of such flats and specimens in the Diana Maria opencast section of the mine can be seen in Mining Operations and Specimen Recovery Photo Archive, Rogerley Mine.
During the opencast mining phase at Diana Maria, the five pockets that were excavated were named Graeber Jones; Snowstorm; Pavel's; Emerald Peaks and Green Hill. To continue extracting specimens by opencast methods beyond this point was becoming uneconomic due to increasing volumes of overburden associated with steepening contours of Fatherley Hill. At this point the operation shifted to underground.
In spring 2019, exploratory work began on the River Catcher vein, some 35 m to the north of the Sutcliffe vein in Rogerley quarry. Clearing of the area around the vein outcrop began in April 2019 (Figure 6) and the early stages of collecting during May 2019 indicate the fluorite is predominantly yellow with some purple and green.
The Sutcliffe vein trends in a SW-NE direction, striking normal (at 90°) to the quarry face at Rogerley. From the adit portal, development of the main drive is designed to follow the Sutcliffe vein along strike. By following the vein, tunnelling control is maintained to target the more richly mineralised zones and reveal adjacent flats. This is different to a large-scale commercial metal mining where the main shaft and development is kept outwith the orebody and in the country rock.
In late April 2018, the quarry face adjacent to the Sutcliffe vein was scraped back of all unstable material using a hydraulic excavator and then hand cleared of any remaining smaller loose debris. Having excavated a shallow recess in the quarry face, a pre-engineered RSJ portal was positioned using a large hydraulic excavator jib. Photos of these operations can be seen in the Mining Operations and Specimen Recovery Photo Archive, Rogerley Mine area of this website.
The RSJ portal was then clad with timber and further protected by careful placement of graded rubble and boulders between it and the quarry face. To ensure slope stability, the boulders surrounding the mine entrance were carefully placed to maintain an angle lower than their angle of repose. This is the maximum angle at which a slope of loose rock is stable.
With all safety measures in place and inspections complete, drilling into the rock face could begin; this was the start of the Diana Maria underground phase.
Drive and cross-cut development are advanced using standard compressed-air rock drills with air-legs. Short rounds are drilled, charged and detonated to minimise shock to nearby mineralised pockets. Mucking out is by a track mounted EIMCO Model 12B rocker shovel. This machine, colloquially termed a 'mucker', is a rail-mounted pneumatic powered shovel that is used to quickly remove the blasted rock debris. The machine is controlled by a miner standing on a side-mounted narrow platform and is driven towards the rock face to fill the front shovel bucket. Once full, the unit is reversed and the bucket swings 180 degrees back over the unit to discharge its load into a waiting ore wagon, attached to a mine loco.
Although the overburden is minimal compared to deeper mines, its thickness does increase as the adit advances further under towards Howley Crag on Fatherley Hill. The overburden, consisting of well indurated limestones interbedded with thin shale, forms a weak overall rock mass due to shale partings, pervading open joint patterns and clay infilling. The limestone and ironstone have well defined bedding and vertical fracturing as a result of tensile failure during uplift contemporaneous with emplacement of the Weardale granite.
Once the mine working is excavated, the new void space acts as a sink to natural water flow within the hill and the increased flow rate weakens the more friable and water-reactive lithologies. Clay-filled joint planes gradually deform under stress once sections are developed or stoped-out and as a result, continuous roof support is required throughout the mine. In the early mining operations, arched rolled steel joists (RSJs) were installed with timber planking between them. In the current operation, square timber legs and beams are installed every 1.2 m, with timber boards in the roof where required.
Good airflow through the mine is essential not only to remove fumes following blasting, but because of the continuous entry of small levels of radon gas emanating from the Weardale granite some 400m below. Vertical fracture networks connect the granite to surface and hence the mine workings. Radon levels within the mine are constantly monitored to conform with HM Inspectorate of Mines standards.
Mineralised flats are extracted using a variety of both hand and power tools, but always by specialised mineral recovery miners, not development miners. Every size of hammer, rock chisel and prybar are employed, including nylon prybars strong enough to remove the tenacious viscous clay that surround specimen material, but non-damaging due to their plastic properties and low hardness.
As all mineral collectors know, great specimens frequently have no accessible face by which to begin extracting them. To overcome this, powered rock splitters and chain saws are used.
The rock splitter is a hand-held, hydraulically powered tool used for the delicate operation of specimen recovery, where conventional drilling and blasting techniques would destroy the fluorite specimens. The tool can be carefully manoeuvred by a skilled specimen miner to remove rock from around a pocket or mineralised vein, so the specimen can be extracted fully intact and without any damage. The narrow cylindrical probe is inserted into either a predrilled hole or natural fracture and under hydraulic pressure the probe expands causing the solid rock to gently fracture or for a crevice to expand. The probe can apply a force in excess of 400 tons (406,000 kg), but with minimal movement, no vibration and dust-free. All rocks are strong in compression but comparatively weak in tension.
A hydraulic powered diamond chain saw is used for the precision cutting and trimming of the rock. The diamond impregnated teeth quickly cut through all the rock types encountered in Rogerley. It is used both in the mine to cut specimens from the surrounding rock and at surface to trim specimens free of excess matrix. In the models we use underground, although hydraulically driven, the hydraulic power unit is pneumatically powered, so that air is vented to atmosphere and not fumes of any sort.
The information provided on this website relating to mining in Weardale, Rogerley Mine and Diana Maria Mine is drawn from many sources. All referenced literature is listed at the end of each article, together with some additional useful references so providing a more general bibliography.
The current mining company, UK Mining Ventures Limited took over from the U.S.A. based UK Mining Ventures LLC, operated by Cal and Kerith Graeber and Jessie and Joan Fisher. Throughout this period Jessie Fisher methodically documented every aspect of mining activity, from mine development to specimen finds and some of his excellent articles are cited in the References. However, special thanks are made to Jessie for the vast amounts of detailed information he has supplied to UKMV Ltd., specifically to Phil Taylor who has been responsible for the website content. Jessie generously provided many specimen photos; pocket discovery information; detailed diary records and copies of the various published articles he has made over the years. As this website evolves, we hope to add more from Jessie’s archives as they provide an important addition to the history of mining in Weardale.
All employees of both UK Mining Ventures Ltd. and Crystal Classics Fine Minerals who have contributed their own photos and or information are thanked. Bryan Swoboda of Blue Cap Productions has filmed at several the UKMV mining operations and his excellent photos and videos are scattered throughout these webpages.
Jolyon Ralph of mindat.org is thanked for creating the original draft of this website, from which it has since evolved as new concepts and information have come forward.
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