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FACETIPS – A GEM CUTTER’S NOTEBOOK

by
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: May, 2019

Rhodochrosites

Posted by Site Moderator Webmaster on Friday, May 24, 2019, In : Faceting 

Duncan Miller





These are the rhodochrosites (presumably from Hotazel) that I have been faceting, on and off, for the past two months. The ‘pink’ stones (on the left) are 0,65 ct; 0,68 ct; 1,46 ct; and 0,96 ct.  The ‘red’ stones (on the right) are 1,39 ct; 1,66 ct; and 1,71 ct. The rough was acquired more than twenty years ago as a small batch of broken and half-finished stones. A recent article about faceted rhodochrosite in The Journal of Gemmology inspired me to try to resurrect them...


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WHO CUT THAT STONE, OR WHAT IS A GEM CUTTER WORTH?

Posted by Site Moderator Webmaster on Friday, May 24, 2019, In : Faceting 
Duncan Miller

The photograph here is of a magnificent 164,11 ct spodumene (variety kunzite) in the collection of the Smithsonian Institution, USA (https://geogallery.si.edu/10002906/spodumene-var-kunzite).


The accompanying text credits the mine at which it was found (in 2010 at the Oceanview Mine in Pala, California), the funds with which it was acquired (Tiffany & Co. Foundation endowment in 2012), and the photographer (Greg Polley). So who cut this stone? This is like acknowledging the ar...


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FACETIPS A simple Emerald Cut

Posted by Site Moderator Webmaster on Thursday, May 9, 2019, In : Faceting 

Duncan Miller

The Emerald Cut is not a meetpoint design so cutting stones with repeatable proportions and facet widths involves guesswork. The following sequence for cutting pavilion and crown avoids most of the guesswork and enables you to cut pairs or sets of matched stones. This sequence is modified from FACET DESIGN Vol. 4 by Robert Long & Norman Steel, in turn based partly on FACETING FOR AMATEURS by Glenn & Martha Vargas. This example uses 5° steps for the three pavilion tiers, but you ...


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WHAT IS A PSEUDOMORPH, AN EPIMORPH OR A PARAMORPH?

Posted by Site Moderator Webmaster on Thursday, May 9, 2019,

According to https://en.wikipedia.org/wiki/Pseudomorph:

“In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form (crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another. The name literally means "false form". Terminology for pseudomorphs is "replacer after original", as in brookite after rutile.

A paramorph (also called allomorph) is a mineral chan...


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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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