New Gem Minerals Update 28 May 2021

28 May 2021

THE inclusion of gem minerals in a mineral collection certainly adds something special. Friends eager to see your collection, even if they have little knowledge of the subject, immediately relate to gemstones because of their association with jewellery.

Gem minerals can add colour and visual appeal to a collection, but best of all provide a window into some of the fascinating geological processes in which they have formed. Pegmatites, skarn deposits and hydrothermal veins immediately come to mind.

Probably most of the species featured today, Beryl, Spodumene, Topaz, Tourmaline and even Spessartine Garnet have been mined from granite pegmatites, a common source for gemstone minerals. The formation of any mineral can only occur once there is sufficient concentration of the elements it requires. Pegmatites are by nature the final phase to crystalise and solidify when a granite or other intrusive igneous rock is emplaced deep beneath the Earth’s surface. As the granite slowly cools and begins to solidify, minerals such as Quartz, Feldspar and Mica have elements in abundance from which to grow, whereas the ingredients for exotic gem minerals remain sparsely scattered throughout the melt. Gradually metals and metalloids such as aluminium, beryllium, boron, lithium, niobium and tantalum begin to concentrate as they are expelled from the ever reducing mobile phase. Eventually the only remaining molten rock is that which will now solidify to form the pegmatite. In this is now a sufficient concentration of elements and water, rich enough to coalesce and crystallise into the gem minerals we covert so much.

Emerald, the green gem variety of Beryl is one of the most well-known gemstones and we have a beautiful small cabinet specimen from the Krupskoye deposit in the Middle Urals of Russia. Translucent to semi-transparent crystals of bluish-emerald green Emerald richly pervade a sharply contrasting matrix of sparkling black Biotite schist. Numerous crystals cover the specimen and on the reverse side a 6 x 3 cm spray of hexagonal Emerald crystals almost cover the specimen.

Also whilst with Beryl, the fanned spray of gemmy prismatic Aquamarine crystals from the Shigar Valley in Pakistan is certainly worth a look. Transparent prisms grading from gemmy vibrant sky blue to a translucent pale sky blue base create a stunning miniature.

We have three excellent and very different Topaz crystals; one from the Murzinka mine in the Middle Urals; one from Katlang in Pakistan and a magnificent pair of pale cornflower blue and pink champagne crystals on Albite from the classic Volodarsk-Volynskii pegmatites in the Ukraine. That from Murzinka is a razor-sharp bright cornflower-blue single crystal, while that from Katlang is a delicate salmon pink champaign with a brilliant glassy lustre.

The name Tourmaline covers a group of crystalline boron silicate minerals of which there are now at least well over 20. Most of the colourful Tourmaline specimens offered for sale tend to be the species Elbaite, but when this is not known for certain the general group name Tourmaline is applied. One different species we have today is Uvite, one of the rarer Tourmalines. The collective name Tourmaline is also useful because the actual species may change within one single crystal due to differing concentrations of elements, manifested by changes in the crystal’s colour.

There are 11 Tourmaline specimens to investigate today. There are several localities from Brazil which include Araçuaí, Brumado, Cruzeiro, Mutuca, Sapo and Taquaral; two beautiful specimens from the Himalaya mine at Mesa Grande in California; one from Skardu in Pakistan and an unusual rich leaf green 9.1 cm long prism from Ndola in the Copperbelt Province of Zambia. That from the Mutuca mine is a stunning blue and green Elbaite measuring 5.7 cm long. It has an exquisite intense chrome green prism with a 1.5 cm deep indigo gemmy termination. The Tourmaline from Taquaral has an outer rind of mid-lime green surrounding a thick inner core of glassy deep bottle-grass green. Two of the dominant terminated faces are beautifully patterned with a most unusual mix of frosted and lustrous intergrown triangular markings, different to, but reminiscent of Widmanstätten patterns in meteorites.

I must also mention an Elbaite from the Himalaya mine in San Diego County. This is what I term a traffic light Tourmaline as the prism changes from pinkish red through lemon amber to vibrant rich lime green. A thing of beauty indeed.

Other super specimens to look at include two Spessartine Garnets from Pakistan; a fantastic cluster of Zircons from the Norwegian island of Seiland; a crystallised gemmy Hiddenite Spodumene from the Adams Hiddenite & Emerald mine in North Carolina and a lovely Quartz Amethyst from the Zillertal valley in Austria. Hey, I almost forgot the gorgeous cranberry red Ruby from Mogok!

The mineralogy and geology of gemstones is a fascinating area of our beloved hobby and one in which modern research continues to amaze. Here in the UK we now have a three day holiday weekend, so there should be plenty of time to contemplate today’s selection of gem minerals and see if any will conveniently slot into your collection. Have a great weekend.

Here is what you have to look forward to in next week's update:

Tuesday 1st & Friday 4th June - Tsumeb

                                         

If you'd like to see a video of any of the specimens listed above then please contact us at orders@crystalclassics.co.uk and we'll be happy to assist you. We endeavour to respond to all enquires within 24 hours during weekdays, however at the weekend it might take us a little longer to respond.

 

The Crystal Classics Summer Open Day will be taking place on Saturday, June 12.

Our beautiful showroom in East Coker, Somerset will be open from 10am to 5pm and will be packed with thousands of fine and rare minerals. There will be many specimens from new, recently purchased collections as well as many fresh Fluorite finds from our mines in Weardale, County Durham.

A delicious breakfast and lunch will also be provided by The Village Cafe which is located next door to our offices.

To book your place please email Debbie at debbie@crystalclassics.co.uk or by phone 01935 862 673 to register your interest.

COVID-19 guidelines will be in place during the day and the following is expected of all visitors:

- Face masks must be worn at all times
- Social distancing must be carried out
- You must wash your hands upon entry to the showroom (in addition there will be several hand sanitiser dispensers provided throughout the building)

It promises to be a great day and we look forward to welcoming you all.

 

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MINERAL WISH LIST

We also offer an additional service that enables you, as our customer, to contact us via orders@crystalclassics.co.uk with your mineral wish list to enhance your current collection, but are unable to find the right specimens on our website. We have 1000's of specimens in our general stock that do not appear online.

Author: JH
Categories: Updates

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