From mid-2021, newsletter articles are no longer posted separately here. Interested readers should scan through the newsletter headings under the ‘Newsletters’ tab.


Duncan Miller

The faceting articles published over the past few years in the Mineral Chatter have been compiled into a single 128 page document, available for download for those interested in saving all the articles together. To download the pdf file click here.

A 29,18 ct cuprite from Onganja, Namibia, cut by Duncan Miller and now in a private collection in Germany.

Browsing Archive: February, 2012

ICELAND SPAR - Did the Vikings Use It for Navigation?

Posted by Site Moderator Webmaster on Sunday, February 19, 2012,

by Eric Greene

Iceland spar is a clear, transparent, colorless crystallized variety of calcite (calcium carbonate, CaCO3). Large pieces are split along natural cleavage planes to form natural rhombs. Iceland spar is probably best known for exhibiting the optical property of double refraction - so, anything viewed through the crystal appears double. It has many uses, in everything from precision optical instruments to LCD screens, and was even used during WWII to make bombsights. The pe...

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Mineral of the month - Coronadite

Posted by Site Moderator Webmaster on Sunday, February 19, 2012, In : Mineral of the Month 

We are pleased to inform you that the mineral coronadite has just been identified at the Rosh Pinah Zinc Mine for the first time. 
It is a predominantly lead based mineral with the formula Pb (Mn4+, Mn3+)8O16. It is monoclinic, with a hardness of 4½-5, and a member of the Cryptomelane Group. Its morphology is massive, with boytroidal crusts with a fibrous structure. It was first identified as a mineral in 1904, and is named after Francisco Vasquez de Coronado (ca. 1500-1554), the first Sp...

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