New British Update 28 June 2022

28 June 2022

AS promised, we return to minerals from the British Isles for both of this week’s updates. The emphasis today is on classic rather than unusual species, although we do have some interesting localities which rarely feature, for example, Blue John Fluorite from Witch’s Cave, Treak Cliff Cavern; Prehnite from Loanhead quarry near Glasgow and a super miniature Blister Copper from Carharrack, just east of Redruth.

One locality very familiar to collectors in the UK is Warden Point on the Isle of Sheppey, although if you are based outside the UK, the few mineral localities of South East England may not yet have appeared on your radar! Warden Point is known for its stellate bursts of white Baryte on microcrystalline, apricot Calcite, you will see a fine specimen amongst today’s selection.

Let’s begin our review in Devon, a mineral-rich county adjacent to Cornwall, but often overshadowed by its more famous partner! The two counties are inextricably linked by the underlying Cornubian batholith, a granite body which gave rise to the majority of mineral wealth in the region. As we have often mentioned, the batholith manifests at surface as several large plutons with many much smaller satellite branches. An example in Cornwall is the Carnmenellis pluton with granite offshoots such as St. Agnes, Carn Marth and Carn Brea. The main pluton in Devon is Dartmoor and one of its famous offshoots crops out at Meldon, a locality occasionally featured in these updates. Today’s specimens feature excellent teal blue Scorodite crystals from Hemerdon mine at Sparkwell north of Plymouth; gemmy, golden-yellow to colourless Baryte crystals from Peak Hill at Sidmouth and a charming miniature of lenticular Siderite on milky Quartz crystals from Virtuous Lady mine by the beautiful village of Buckland Monachorum.

Also from Virtuous Lady, I think, is a splendid capped Quartz; a specimen in which a terminated Quartz crystal is accompanied with a epimorph cap, both of which perfectly mesh. I think it’s from Virtuous Lady mine because the specimen is labelled Cross Fell in Cumbria. We have left the label as Cross Fell, but add the caveat it is most likely Virtuous Lady. If anyone knows of capped Quartz from Cross Fell I will be all the wiser, if you would be so kind as to let me know. Be it from Cumbria or Devon, it’s an excellent example of this fascinating morphology.

The two specimens representing Scotland are the already mentioned Prehnite from Loanhead quarry at Beith and a terrific miniature of tiny, yet perfect Pyromorphite crystals from Laverock Hall Vein at Leadhills in South Lanarkshire. Loanhead quarry was very popular with British collectors throughout the 1980s and 90s, for as an operating quarry, good new material was always readily available to collect. This, plus the distinct advantage of the operator’s most welcoming policy towards collectors. Prehnite is one of the mineralogical features of the Clyde Plateau Tertiary Volcanics, its basalt being mined at Loanhead quarry. This acidic lemon yellow small cabinet specimen is a striking example.

Returning to South West England and into Cornwall, the Natrolite from Dean quarry near St Keverne on the Lizard Peninsula is a superb, clean example; just one of several zeolites occurring in the quarry. The Natrolite forms opaque, snow white acicular crystals to 2.5 cm, often becoming colourless and quite gemmy towards their terminations. They cover a thin plate of 1 to 2 mm gemmy Calcite crystals.

Other Cornish specimens include a chunky crystallised Chalcopyrite from the Redruth mining district; Olivenite with Quartz and a Pharmacosiderite, both from Wheal Gorland; a tetrahexahedral Fluorite on Quartz crystals from St. Agnes, possibly Pell mine; a Sphalerite displaying a beautiful violet-mauve patina, also from St. Agnes; Blister Copper-habit Chalcopyrite from Carharrack mine, Redruth and finally, a stunning, complexly crystallised Galena labelled simply “Cornwall, England”. Most aware of sticking my neck out, I suggest this is from Herodsfoot mine at Lanreath, a mine known for its many various habits of Galena. Mirror-bright octahedral crystals with nested triangular faces up to 1.3 cm cover a foliated Killas matrix; Killas being a Cornish mining term for a metamorphic rock of sedimentary origin. The Galena crystals are happily interspersed by ribbons of small, drusy Quartz crystals, another quite characteristic feature of Herodsfoot specimens. Again, I stand to be corrected if anyone considers a different locality more likely.

Let’s conclude with a round-up of specimens from around Northern England. From West Cumbria we have Quartz with Hematite from Frizington; Quartz with Hematite and Calcite from Cleator Moor; teal blue Baryte crystals with reddish-creamy Dolomite crystals, Frizington; a Witherite coated with Baryte from Nentsberry Haggs mine, Alston Moor and golden lemon Fluorite with Siderite and Calcite from Hilton mine in Scordale.

Last but not least is the Blue John variety of Fluorite from Blue Cliff Vein in Treak Cliff Cavern, near to Castleton in Derbyshire. This small cabinet specimen is especially good as it exhibits intergrown cubic Fluorite crystals on top. Crystals are seldom a feature of Blue John as it is better known for its polished banded slices and artisan-crafted objects; jewellery, bowls, goblets, for example.

Incidentally, for anyone interested in UV minerals, do check out the Sidmouth Baryte and Nentsberry Haggs’ Witherite with Baryte; they are both pretty good under long wave.

That’s a complete overview of all 21 featured today. For any specimen you are keen to know more about, use the hyperlinks to see additional photos and a full, detailed description together with specimen dimensions. Enjoy exploring and you may find just what is needed to fill some specific gap in your British suite. See you same time, same place, on Friday. PT.

                                         

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Author: JH, PT
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