Difference between revisions of "Garnet"
From The Gemology Project
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+ | {{edit|--[[User:Doos|Doos]] 06:18, 8 December 2006 (PST)}} | ||
+ | |||
{{garnet}} | {{garnet}} | ||
− | Garnet is a | + | Garnet is the family name given to a series of members, with a common crystal habit and slighly different chemical make-up ([[Isomorphous_replacement|isomorphous]]). The following are the 6 members of the garnet family: |
+ | * Pyrope | ||
+ | * Almandine | ||
+ | * Spessartite | ||
+ | * Uvarovite | ||
+ | * Grossular | ||
+ | * Andradite | ||
+ | |||
+ | According to similarities in the chemical composition, we can divide the above members of the garnet family into two groups. | ||
+ | |||
+ | * PyrAlSpites (Pyrope, Almandine, Spessartite) | ||
+ | * UGrAndites (Uvarovite, Grossular, Andradite) | ||
+ | |||
+ | All the above members are rarely found with an ideal chemical make-up, instead they form isomorphous series. Most gem quality garnets belong to either of the following 5 isomorphous series and their chemical composition is an intermediate between the two endmembers mentioned. | ||
− | Almandine | + | * Pyrope-Almandine |
− | Pyrope | + | * Pyrope-Spessartite |
− | Grossular | + | * Spessartite-Almandine |
− | + | * Pyrope-Grossular | |
− | Andradite | + | * Grossular-Andradite |
− |
Revision as of 07:18, 8 December 2006
This section is currently under construction, do not edit until this message is gone | |
--Doos 06:18, 8 December 2006 (PST) |
Garnet | |
---|---|
Chemical composition | L3M2(SiO4)3
Isomorphous series |
Crystal system | Cubic |
Habit | Dodecahedra |
Cleavage | None |
Hardness | 6.5-7.5 |
Optic nature | Isotropic |
Refractive index | 1.74-1.89 |
Birefringence | None |
Specific gravity | 3.60-4.20 |
Lustre | Vitreous to sub-adamantine |
Garnet is the family name given to a series of members, with a common crystal habit and slighly different chemical make-up (isomorphous). The following are the 6 members of the garnet family:
- Pyrope
- Almandine
- Spessartite
- Uvarovite
- Grossular
- Andradite
According to similarities in the chemical composition, we can divide the above members of the garnet family into two groups.
- PyrAlSpites (Pyrope, Almandine, Spessartite)
- UGrAndites (Uvarovite, Grossular, Andradite)
All the above members are rarely found with an ideal chemical make-up, instead they form isomorphous series. Most gem quality garnets belong to either of the following 5 isomorphous series and their chemical composition is an intermediate between the two endmembers mentioned.
- Pyrope-Almandine
- Pyrope-Spessartite
- Spessartite-Almandine
- Pyrope-Grossular
- Grossular-Andradite