Beginner's Guide to Gemmology by Peter G. Read

By Peter G. Read

Show description

Read or Download Beginner's Guide to Gemmology PDF

Similar mineralogy books

Mine Safety: A Modern Approach

The excessive variety of deadly injuries within the mining makes mine security a massive factor during the global. the dangers to existence are common, starting from airborne dirt and dust explosions and the cave in of mine stopes to flooding and normal mechanical blunders. Mine defense combines unique info on protection in mining with tools and arithmetic that may be used to maintain human existence.

Chemistry, Process Design, and Safety for the Nitration Industry

This is often the 3rd ACS Symposium sequence ebook facing nitration, the 1st having been released in 1976 and 1996. the character of this 2013 book displays the adjustments world wide in method protection administration, and geographies of analysis and production. The contributions to this e-book have been first provided on the 243rd ACS nationwide assembly in San Diego, California in March of 2012, within the commercial and Chemical Engineering department.

Extra info for Beginner's Guide to Gemmology

Sample text

Elements of symmetry So far, t h e adjectives 'regular', ' s y m m e t r i c a l ' and ' p a t t e r n ' have all been used t o describe a crystalline s u b s t a n c e . In crystal­ lography, t h e c o n c e p t of s y m m e t r y as applied t o t h e crystal structure is very i m p o r t a n t . F o r m o s t gemmological w o r k it is sufficient t o be able t o recognise t h e gem crystal h a b i t s , a n d t o be aware of their associated optical characteristics. However, CRYSTALLOGRAPHY 38 t h e three elements of symmetry are f u n d a m e n t a l t o t h e s t u d y of crystallography, and are defined here for t h e sake of completeness.

Often used t o describe a t y p e of inclusion (as in moss agate and green tree agate). This is a form whose faces intersect t h e vertical axis and o n e h o r i z o n t a l axis, b u t are parallel t o t h e third axis. This is a g r o u p of similar crystal faces. g. t h e garnet g r o u p ) . g. t h e garnets). g. graph­ ite and d i a m o n d ; andalusite, k y a n i t e and silHmanite). A crystalline s t r u c t u r e c o m p o s e d of straight or curved plates or leaves. R o u n d e d intersecting c o n t o u r s ( e .

1. T h e table includes t h e g e m s t o n e species c h a l c e d o n y , j a d e i t e , n e p h r i t e a n d t u r q u o i s e w h i c h are classified as crypto-crystalline. This t y p e of mineral has g r o w n n o t as a single large crystal b u t as an aggregate of small or microscopic crystals (or crystalline fibres) r a n d o m l y o r i e n t e d within t h e b o d y of t h e gem. F o r this reason, t h e h a b i t of crypto-crystalline minerals is always massive, a n d t h e gems are mainly semi-translucent or o p a q u e .

Download PDF sample

Rated 4.19 of 5 – based on 46 votes