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Orange Grossular Garnet

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librarychickie

Shiny_Rock
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Can someone tell me exactly what it is? I have found one that I really like the color and cut of; however, what makes it different from a Spessartite?

Thanks for the input!

~LC
 

ma re

Ideal_Rock
Joined
Aug 10, 2008
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Chemistry. Spessartite is one of the aluminium group garnets and grossular is from the calcium group garnets. Not that I know so, but I googled it out in like 2 minutes
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Details are available at: http://www.palagems.com/spessartite_buyers_guide.htm
 

Richard M.

Brilliant_Rock
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Date: 2/23/2009 9:19:15 AM
Author:librarychickie
Can someone tell me exactly what it is? I have found one that I really like the color and cut of; however, what makes it different from a Spessartite?


Thanks for the input!


~LC
Hi,
Grossular and spessartite garnets are different species. Both are aluminum silicates. Grossular is a calcium garnet and spessartite is a magnesium garnet. Both are members of the garnet group and while they crystallize in the same form (cubic) each species has different physical properties. There are some 20 known garnet species but only 5 of them (if you don''t count cross-species mixtures like "rhodolite" and "malaia") are used as gems. Green uvarovite druses are currently being cut for gem use so maybe we could say 6 species are used.

Grossular garnets have the widest color range of any gem garnets. Grossular is the only garnet species that occurs pure or near-pure outside the laboratory, so colorless or near-colorless grossulars are known. The species gives us tsavorite, mint garnet as well as orange-brown hessonite and many other hues: yellow, orange, orange-red, peach, pink in many shades. The pale green color of some grossulars reminded people of gooseberries, so that''s how the species got its name (Latin ''grossularia'').

Spessartites and grossulars differ in brilliance. Spessartite has a refractive index of 1.79 to 1.81, making it among the most brilliant of orange gems; grossular has an R.I. of 1.73 to 1.76. There are other differences in density and typical inclusions.
Richard M.
 

Catmom

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Thank you so much Richard! That was very interesting and something I didn''t know about garnets.
 

Richard M.

Brilliant_Rock
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I can''t figure out how to edit posts but I made a mistake above. Spessartite is a manganese, not magnesium garnet. My coffee-deprived brain got the two mixed up.
Richard M.
 
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