Showing category "Mineralogy" (Show all posts)

DIGGING OUT DUMORTIERITE

Posted by Site Moderator Webmaster on Saturday, September 26, 2020, In : Mineralogy 

I do give myself complications.

Based on the success of the “September Spheres”, we invited photos of “royal blue” minerals for our October newsletter. This is because we are featuring Peter’s detailed article on lapis lazuli. Ultramarine is such a rich colour and there are not that many minerals of such a classic blue.

For my contribution, I photographed the few possibilities I had in my mineral cabinet, but thought a bit more. There was an odd offcut of stone in the outside cupb...


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LAPIS LAZULI: EAST VS WEST

Posted by Site Moderator Webmaster on Friday, September 25, 2020, In : Mineralogy 

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

Posted by Site Moderator Webmaster on Sunday, August 23, 2020, In : Mineralogy 

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

Posted by Site Moderator Webmaster on Monday, July 27, 2020, In : Mineralogy 

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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TIME

Posted by Site Moderator Webmaster on Thursday, June 25, 2020, In : Mineralogy 

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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The World of Tourmaline (in brief)

Posted by Site Moderator Webmaster on Thursday, June 25, 2020, In : Mineralogy 

Peter Rosewarne

I’ve borrowed the title of a new coffee table book by Gerhard Wagner for this article as it seems appropriate in that the Tourmaline Group encompasses some 14 species currently and it is found in classic localities around the world. The idea for doing this article came from a comment from Jo that EXCO had raised tourmaline as a possible discussion topic. I also have and have had quite a few tourmaline specimens in my collection over the years and have attempted to limit dis...


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BLUE LACE AGATE FROM YSTERPUTS, SOUTHERN NAMIBIA

Posted by Site Moderator Webmaster on Sunday, May 24, 2020, In : Mineralogy 

by Jo Wicht and Duncan Miller

For several decades small mines in southern Namibia have produced an attractive banded agate marketed as lapidary material. The major source has been a mine on Ysterputs farm, producing blue lace agate. It was promoted widely by the late George Swanson who owned the mine, so this material with its wavy blue and white lines is quite familiar. What is less well known is that the blue lace agate from Ysterputs is accompanied by several minerals forming aesthetic, c...


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SOME REFLECTIONS ON STARTING A MINERAL SPECIMEN SALE WEBSITE

Posted by Site Moderator Webmaster on Tuesday, March 24, 2020, In : Mineralogy 

by Peter Rosewarne

 About a year ago I wrote an article on selling a mineral collection from South Africa, which was featured in the MinChat. One of the methods I listed, unsurprisingly, was setting up my own internet site. I didn’t go that route initially, relying on selling back specimens to dealers such as Hummingbird Minerals, John Betts Fine Minerals, Fabre Minerals and The Mineral Gallery, and some on Club Open Days. However, the former route seems to have run its course in terms of ...


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KYAWTHUITE, THE RAREST MINERAL, FOR NOW…

Posted by Site Moderator Webmaster on Wednesday, September 25, 2019, In : Mineralogy 

Duncan Miller


Reproduced by courtesy of the Natural History Museum of Los Angeles County

Every year, the International Mineralogical Association approves the names of many newly discovered minerals (http://nrmima.nrm.se//recentmin.htm). The requirements are stringent, involving analytical descriptions of both the chemistry and physical structure of any candidate new mineral. Most of these are microscropic and not display-worthy. But every now and then, a new mineral is discovered that not only ...


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Zultanite - A relatively new gemstone from Turkey

Posted by Site Moderator Webmaster on Monday, June 24, 2019, In : Mineralogy 

By Peter Rosewarne

My wife and I recently visited Istanbul for a few days on our way to Venice and beyond. An 11-hour non-stop flight on Turkish Airways from Cape Town International Airport got us there. Impressions of Istanbul were favourable; interesting, friendly, good food, clean and safe. We stayed in the Old City and did a lot of walking and had an obligatory tourist boat ride along the Bosphorus (East meets West). We visited the Grand Bazaar, the largest covered bazaar in the World with...

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Ye Olde English Spar Boxes – a Hobby Revived!

Posted by Site Moderator Webmaster on Monday, June 24, 2019, In : Mineralogy 
Lesley Andrews

During the nineteenth and early twentieth centuries a popular pastime among the mining population of Northern England was the construction of spar boxes. These were used to decorate their homes, and also to sell to make some extra money. Spar boxes were made up of various crystals (spar is the old name for a crystalline mineral) which were collected by the miners working in the lead and iron mines of the north Pennines and Lakeland areas.

My first encounter with spar boxes in 200...


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Phlogging a dead horse?

Posted by Site Moderator Webmaster on Thursday, May 9, 2019, In : Mineralogy 
Jo Wicht

Many of you are aware of my obsession with Blue Lace Agate, both from a lapidary point of view and with stones from the mine, as well as my curiosity as to how the mineral was possibly formed. Any new information that I come across, be it a new specimen or comment, has to be investigated. Recently it was Marco Campos-Venuti’s new book (Banded Agates: a genetic approach (2018) www.agatesandjaspers.com) which set me off on the trail again because it has a chapter on Lace Agates. Marco...


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