LAZURITE – A TUCSON STORY

September 26, 2020

I first visited the Tucson shows in 1992. My intention was to buy faceting rough, but there was almost none I could afford, although the rand/dollar exchange rate was 6:1. One day, walking around with my friend and research colleague David Killick from the University of Arizona we wandered around, dazed and bewildered by the spectacular minerals from Afghanistan on display in one of the numerous tented venues. On one table, crowded with Afghan ethnic jewellery, possibly all modern, there sat one specimen of blue lazurite in calcite matrix. David and I had never seen one of these outside of a book illustration, so we oh’d-and-ah’d over it, and the Afghan man tending the table thought he may have a sale. I explained that I wasn’t looking for mineral specimens, and we walked away. Sometime later our wandering brought us back to the table with the lazurite. The specimen had been joined by a few others, so in all innocence we gawked again. Once more we walked away. On our third arrival, the owner got tetchy and pointed out that we obviously were interested and why didn’t we buy. So the haggling started and he brought out a few more specimens, six in total, two quite battered and small, the others rather nice. Eventually he said, “Look, I deal in ethnic jewellery not rocks. I don’t want these. You can have all of them for $300.” Done! So I came home with almost no gem rough but several Afghani lazurites. I gave the smallest ones away, but still have four in their typical calcite matrix. DM

  

  
Lazurite (haüyne), Sar-e-Sang, Afghanistan: width of matrix specimens 60–85 mm

WHAT’S IN A NAME?

The lazurite we love (Na6Ca2(Al6Si6O24)(SO4,S,S2,S3,Cl,OH)2), not to be confused with lazulite (MgAl2(PO4)2(OH)2), appears to be a sulphide-rich variety of haüyne ((Na,K)3(Ca,Na)(Al3Si3O12)(SO4,S,Cl)) and part of the Sodalite Group, according to Mindat (https://www.mindat.org/min-2357.html

 

LAPIS LAZULI: EAST VS WEST

September 25, 2020

Peter Rosewarne

And now for something completely different, from me at least. I don’t normally write about semi-precious ornamental stones/rocks but felt there was a story in this one based on a long-ago overseas trip, a more recent article in the Mineralogical Record, some carvings I have from the former and some mineral specimens related to the latter.

Firstly, some technical clarity about lapis lazuli, or ‘lapis’, which many of you probably don’t need. I had always thought that ...


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PLAYING WITH QUARTZ SPHERES IN POLARISED LIGHT

August 24, 2020
Duncan Miller

It’s play time!  For this exercise you need a flat computer screen with an open blank Word page, a smallish clear quartz crystal, a quartz sphere if you have one, or if not, some clear quartz beads (glass beads won't work), plus a pair of cinema 3D glasses or Polaroid sunglasses. 

Quartz crystals are anisotropic. This means that a ray of light travelling through the crystal is split into two polarised rays, vibrating at right angles to each other. There is only one directio...


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Stories Behind Some Recently Acquired ‘Exotic’ Rocks and Polished Spheres

August 23, 2020

by Peter Rosewarne

With the lockdown in force it’s given me some time to revisit my passion for igneous rocks and their minerals, being what we used to call a ‘min and pet’ man whilst studying geology at Kingston University back in the early 70s. Of particular interest to me on the local scene are the Bushveld Igneous Complex, the Pilanesburg Alkaline Complex, kimberlites, ultramafics and the Vredefort Dome.  In my quest to find specimens of the ‘type’ rocks from these sites, in a...


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RECYCLE, REUSE, REPURPOSE – THE CAPE TOWN TIN MINES

July 27, 2020

Duncan Miller

This month we are going to do all three, recycle an old publication, reuse it with additional photographs, and repurpose it as an article on the club’s website. The article describes Cape Town’s former tin mines, and the website article has a virtual tour of the Vredehoek tin mine on Devil’s Peak, courtesy of Dr Gregor Borg of Halle University in Germany. All of this is available for download from http://ctminsoc.org.za/resources/CAPETOWNSTINMINES.pdf

Few people know that ...


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MINERAL OF THE MONTH – OLIVINE

July 27, 2020
Duncan Miller



Olivine is the name given to both a mineral and a mineral group. The mineral olivine is an orthorhombic silicate with the relatively simple chemical formula of (Mg,Fe)2[SiO4]. It has a continuous range of composition between two end members, one magnesium-rich and the other iron-rich. The magnesium end member of the range is called forsterite (Mg2SiO4) and the iron end member is fayalite (Fe2SiO4). These distinct minerals form part of the olivine group, which also includes a mang...

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FABERGE’S BIRDS

July 27, 2020

Lesley Andrews

Peter Carl Fabergé was born in St Petersburg in 1846, and eventually became Goldsmith to the Imperial Court of Russia, and a supplier of wonderful artworks worldwide. He assumed charge of the workshop his father had established in St Petersburg when he was only twenty-four years old, and presented the first Imperial Easter Egg to the Russian royal family in 1884. The workshop survived until 1918, by which time Russia had succumbed to revolution and the royal family was no mor...


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A GEM CUTTER’S JUNK BOX

June 25, 2020

Duncan Miller

After several years, or after many years, a gem cutter lands up with a junk box. Mine contains disappointing stones abandoned in disgust and partly-worked stones that came over the years with various faceting machines and batches of rough. As a lock-down project I decided to see what I could make from the contents of the faceting junk box. (There are another two – one with cabochons and another with broken synthetics. You never know, you know…)

To make it something of a ...


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A MINERAL COLLECTOR’S SHOW BOX

June 25, 2020

Malcolm Jackson

The Blue Lace Agate article by Jo and Duncan in last month’s Mineral Chatter inspired me to make a box and as I had some really nice pieces of Yellowwood around, I got sawing and made the box you see in the picture. I made the box 300 mm × 400 mm × 100 mm deep. I hope to catalogue the specimens and add some artwork. I also want to include Jo and Duncan’s article in a booklet format.



I wanted to house some of my Blue Lace Agate specimens that I had collected over many...

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TIME

June 25, 2020

Duncan Miller

Our individual lives are so short, and geological time so long, that it is difficult to comprehend ‘deep time’, the most awe inspiring aspect of geology. Geologists often seem to work in units of a million years, as though that is the basic unit for the passage of time on Earth. So let’s make some effort to comprehend geological time – after all it is what makes geology tick.

Consider a rare, long-lived human life span of 100 years. There would be 10 000 of those in a ...


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