A brief guide to minerals from the Lake district

There are in excess of 300 different minerals to be found in the Lake District and surrounding area, and while some merely compose the rocks, there are many that form attractive crystals of varied colour, size and form. The mning of lead, copper, zinc, iron, nickel, cobalt, antimony, manganese, tungsten, Barite and Graphite has produced an array of carbonates, sulphates, silicates, arsenates, phosphates and vanadates of interest to generations of mineral collectors. A few of the minerals that the area is noted for are described below.

Pyromorphite

Pyromorphite from Iron Crag, Roughton Gill Mine. Main crystal is 10mm across.

The Lake District has a number of localities that have produced good quality Pyromorphite specimens that are to be seen in many fine museum collections around the world. During the nineteenth century the famous Roughton Gill Mine on the Caldbeck Fells, produced numerous large specimens in an amazing variety of form and colour, that are still considered to be world class. Right up to the present time crystals in excess of 10mm could still be found with diligence from here and the adjoining Mexico Mine. The continuation of the Roughton Gill vein at Driggith and Sandbeds Mine to the north east, has abundant khaki green Pyromorphite covering large hand size specimens. The crystals are smaller, of the order of 2 to 3mm, and show less variation, but good specimens are still worth having. Outside the Caldbeck Fells, large brown Pyromorphite crystals were discovered in the upper workings at Force Crag Mine in the 1990's. Access to these workings is not currently possible. More recently, Saddleback Old Mine has produced abundant Pyromorphite in a good range of colour and form. Typically the Pyromorphite occurs as pale blocky crystals up to 10mm in length or as prismatic vivid green crystals to 3mm in length, but pink, brown, yellow and lime green crystals also occur. Other noted sites are: Blencathra Mine (pale salmon pink crystals exceptionally up to 6mm); Kinniside Mine (crusts of small but attractive yellow to green crystals); and Old Brandlehow Mine (good coatings of acicular vivid green crystals).

Pyromorphite from Force Crag Mine with crystals to 6mm long.

Pyromorphite from Saddleback Old Mine. Specimen is 30mm across with crystals up to 5mm long.

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Mimetite

Mimetite var. 'Campylite' from Dry Gill Mine. Specimen size is 70x40x25mm.

Mimetite from Dry Gill Mine. Specimen size is 85x60x30mm.

Superb specimens of Mimetite are to be found at Dry Gill Mine on the Caldbeck Fells. Here Mimetite form distinctive six sided rounded crystals of a rich orange-brown to red-brown colour, commonly referred to as Campylite. The deposit was only opened up to a limited extent, but even so is thought to be one of the largest deposits of Mimetite in the world. Green and yellow Campylite also occur, as do a wide range of other crystal forms. Pyromorphite is also found at Dry Gill Mine in lesser amounts but cannot be visually distinguished from the Mimetite. Elsewhere, small pale crystals of Mimetite are found at Brandy Gill Lead Mine, of more interest in its association with Bayldonite, Duftite and Stolzite than the intrinsic quality of the Mimetite. Some of the globular Pyromorphite found at Roughton Gill Mine, in the upper reaches of the gill, is known to actually be Mimetite, but again distinguishing from the more abundant Pyromorphite is not possible without modern analytical techniques. Mimetite has been identified widely around the Caldbeck Fells in association with rare lead and copper arsenates, but may also be more widespread across the Lake District than currently known due to the lack of proper analysis of pyromorphite/mimetite specimens.

Mimetite var. 'Campylite' from Dry Gill Mine. Specimen is 30mm across.

Plumbogummite

Roughton Gill Mine set the standard for the best Plumbogummite specimens in the world for almost 200 years. Only in recent years have finds been made in China of a comparable standard. The best examples consist of cobalt blue crusts of Plumbogummite, which may pseudomorph Pyromorphite, with Pyromorphite crystals scattered over the Plumbogummite. This seems to be a feature not present in the Chinese specimens to date, and in my opinion still gives the classic Roughton Gill material greater aesthetic appeal. Less fine Plumbogummite is also abundant at Dry Gill Mine as turquoise blue crusts with canary yellow acicular Pyromorphite, and as brown pseudomorphs of the Pyromorphite. Plumbogummite from these two localities are easily distinguished from each other but even so examples of Plumbogummite from Dry Gill mislabelled as from Roughton Gill Mine are not difficult to find on the internet. Very small amounts of pale blue Plumbogummite are to be found at Comb Beck with Pyromorphite, Wulfenite, Bayldonite, Duftite/Mottramite, Corkite and Agardite-(Y). There are several other possible localities for Plumbogummite but they await proper analysis.

Plumbogummite with Pyromorphite from Dry Gill Mine. Specimen size is 75 x 60 x 45mm

Plumbogummite pseudomorphing Pyromorphite from Dry Gill Mine. FOV: 25mm

Plumbogummite from Roughton Gill Mine. Specimen size is 50x45x25mm

Calcite

Calcite is found widely across the Lake District, but usually only in small amounts. However, the lead mines around the Patterdale area have long been known to produce attractive Calcite in a variety of crystal habits, and still occasionally do. The other main locality for Calcite is Carrock Mine on the Caldbeck Fells. Calcite is an abundant late stage infilling to the tungsten veins, especially in the northern half of the veins, where it lines vughs and a few E-W bearing fissures. The Calcite from here can also sometimes be dissolved away with great effect with weak acids to reveal the underlying primary minerals.

Calcite from Hartsop Hall Mine. Specimen is approx. 50mm across.

White Calcite crystals from the Greenside Mine

Left & right : Calcite from Greenside Mine. Both specimens are approx. 50mm across

Barite

Cockscomb Barite from Helvellyn Mine. Specimen size is 130x100x80mm

Large tabular Barite crystal from the Dry Gill Mine

Barite from Dry Gill Mine. Crystal is 45mm on edge

Mining for Barite initially started in the 1860's but only really took off in the 20th century. The product was successfully mined at Potts Gill Mine, the Sandbeds Mines, Force Crag Mine, and Ruthwaite Mine, but only Force Crag Mine was noted for producing large white tabular crystals. Barite is abundant in many lead bearing veins in the northern half of the Lake District in the cockscomb habit, especially in the Patterdale area. Specimens can be large and often have a sprinkling of small Chalcopyrite crystals and/or Calcite crystals. Well formed white tabular Barite crystals could be recovered at one time from underground at Dry Gill Mine, but access is no longer possible. Examples on the dumps tend to be broken or bruised. On the western side of the Lake District, the Kinniside Mine has long been known as a source of prismatic glassy pale blue Barite. This is a rare crystal form for the lead mines of the area, but is more common in the nearby West Cumbrian iron mines.

Graphite

Graphite was the most valuable commodity mined in the Lake District. There is only one locality, the Seathwaite Graphite Mine; all other attempts to locate Graphite failed. All of the world's mined deposits of graphite have been formed within sedimentary or metamorphic rocks. The deposit at Seathwaite is unique in being formed within an igneous rock, is of the highest grade, and may have been the first to be commercially exploited. A full explanation of how it was formed has yet to be determined. The latest research into the deposit can be found on the British Geological Survey web site. The Graphite occurs as nodules of varying size within an altered Dolerite or deposited along fractures within quartz veins. Its not the most attractive of minerals but once it was literally worth fighting over.

Specimen size is 150x110x70mm

Hemimorphite

Excellent sky blue botryoidal Hemimorphite was found in abundance at Roughton Gill Mine when it was working. These consist of layer upon layer of crystals of slightly different shades of blue. More typical well formed glassy crystals are also found here, commonly associated with well formed Aurichalcite and Rosasite. Small amounts of the sky blue Hemimorphite are found at the nearby Sandbeds Mine and further afield at Greenside Mine, where it is occasionally formed over cockscomb Barite. Clear crystals of Hemimorphite are found widely across the Lake District wherever Sphalerite occurs in the veins but seldomly as large specimens.

Botyroidal blue Hemimorphite from the Greenside Mine

Hemimorphite from Roughton Gill Mine. Specimen size is 70x50x45mm.

Hemimorphite from the Glencoyne Adit, Greenside Mine. Specimen size is 80x60x50mm.

Alunite, Beudantite and Crandallite Group Minerals

There are particular challenges of identification associated with these minerals. Not only do they form a series with one another, making visual identification of most specimens unreliable, but more than one method of advanced analytical technique may be required to positively identify the mineral. For example, Beudantite specimens from Burdell Gill, confidently reported on the basis of XRD, have recently been re-investigated and are now considered to be Kintoreite and/or Segnitite. So far, Beudantite, Kintoreite, Segnitite, Corkite, Hinsdalite, Plumbojarosite and Plumbogummite have all been confirmed from the Lake District but its very possible that Philipsbornite and Hidalgoite will also be identified. Beudantite is relatively common in some veins on the Caldbeck Fells where it is associated with iron, copper and other lead arsenate minerals, but also more broadly in small amounts across parts of the Lake District. Corkite is found as excellent yellow to black crystals to 2.5mm across in outcrops of the Roughton Gill vein with sugary coatings of Plumbogummite and rare green Mottramite crystals, and similar sized crystals grade into pale blue Hinsdalite at Saddleback Old Mine. These form good pseudomorphs of large Pyromorphite crystals. Corkite-Hinsdalite probably occurs at Force Crag Mine replacing Pyromorphite but requires confirmation as to the precise minerals present. There are similar occurrences at Wanthwaite Mine and elsewhere but are unverified without proper analysis.

Sea green Hinsdalite crystals from the Saddleback Old Mine

Hinsdalite completely pseudomorphing Pyromorphite from Saddleback Old Mine. Specimen is 30mm across with the largest pseudomorph 10mm in height.

Dark brown Corkite crystals on Quartz from the Saddleback Old Mine

Corkite from Saddleback Old Mine. Specimen size is 65x45x45mm.

Corkite crystals from Roughton Gill Mine

Corkite crystals to 1.5mm from Iron Crag, Roughton Gill Mine

Microcrystalline Philipsbornite (?) . FOV 6mm

Plumbogummite -Hinsdalite pseudomorphs of Pyromorphite-Mimetite. Mirehouse Trials FOV 30mm

Plumbogummite-Hinsdalite coating and partially pseudomorphing Pyromorphite. Glenderaterra. FOV 15mm.

2 specimens of Alunite-Beudantite-Crandallite group minerals from the same locality. The variability in appearance suggests several members of the group may be present. FOV 25mm.

Linarite

During the 19th century superb large Linarite crystals were found at Red Gill Mine. Small crystals and broken fragments could still be found here until the 1990's, but now the dumps are virtually barren. There are also large crystals of Linarite in old collections labelled as from Roughton Gill Mine, but modern research on these suggest they were from Red Gill Mine and sold as being from the more famous Roughton Gill Mine. However good small crystals are to be found from here, especially from the higher outcrop workings. Elsewhere, micromounts are widespread in small amounts wherever lead and copper sulphides are found in the mineral veins.

Spray of Linarite crystals to 1.5mm with clear Leadhillite crystals from the Blencathra Mine.

Broad bladed Linarite crystals to 1mm from Dodd End Mine.

Caledonite

Caledonite forms beautifully formed blue-green crystals up to 5mm in length at Red Gill Mine. A specimen from here was used to determine the crystal structure of Caledonite. Small specimens could still be found until the present collecting restrictions came into force, in association with Linarite, Leadhillite, Mattheddleite and other rare lead secondaries. Good quality Caledonite is also known from the nearby Roughton Gill Mine, especially from the upper outcrop workings. More broadly, occasional micromounts are to be found at most the Caldbeck Fells mine sites, the Blencathra-Bannerdale mining area, most of the Patterdale lead mines, Rigghead Quarry, Dale Head Mine and Kinniside Mine near Cleator Moor.

Prismatic Caledonite crystals from Roughton Gill Mine. FOV 12mm

Blocky Caledonite crystals from Red Gill Mine. FOV 6mm

Prismatic Caledonite crystals from Roughton Gill Mine. FOV 4mm

Leadhillite

There's a handful of localities in the Lake District that have produced good Leadhillite crystals; during the 19th century large crystals were found from Red Gill Mine and Roughton Gill Mine, with more recently finds being made at Rigghead Quarry and Greenside Mine. Small crystals in decomposing Galena are more widespread, usually being found wherever Caledonite and/or Linarite occur in the assemblage. The more notable localities include the other Caldbeck Fells mines, Blencathra Mine, Kinniside Mine, and Dale Head Mine where its often overgrown by Mattheddleite.

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An unique find of Leadhillite crystals to 13mm across from Greenside Mine. The lining of the vug and the Leadhillite has a skin of discoloured post-mining Cerussite flowstone(?).