EOSC 118 Lecture Notes - Lecture 14: Hexagonal Crystal Family, Conchoidal Fracture, Topaz
4 Dec 2017
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Document Summary
Beryl = aluminous beryllium cyclosilicate (made of al, be, si + o) Colourless opaque = beryl, colourless transparent = goshenite. Others = morganite (pink, mn replacement), heliodor (yellow, fe3+ replacement), red beryl (mn3+ replacement and no water in channels), Maxixe (irradiation + no3- in channels), emerald (cr3+ or v3+ replacement), aquamarine (fe2+ or fe3+ replacement) Sg + ri vary depending on composition. Long + short wave uv fluorescence observed b/c cr3+ (red) All gem beryl = type i gem (nearly free of inclusions), except emerald = type iii (inclusions = common and often visible) Inclusions in emerald = le jardin ( the garden in french) Beryl = made of tetrahedral sio4 + beo4 sites and octahedral alo6 side. Channels found within 6-membered sio4 rings, and can contain na/water. Substitutions at al produces most colour variations. Emerald = cr3+ or v3+ substitutes for al3+ (originates from metasomatic zones) Finest emeralds have little to no fe.
