Garnet
Silicate · e.g. Fe₃Al₂(SiO₄)₃ · also: Almandine, Pyrope, Spessartine
Garnet is a group of hard silicate minerals that form distinctive many-sided crystals, most often deep red, and used as both gems and abrasives.
What is garnet?
Garnets are a group of related silicate minerals sharing the same crystal structure but differing in composition and colour. The common deep-red almandine is a schist and gneiss mineral, but garnets also come in orange (spessartine), green (tsavorite, demantoid) and more. They form well-shaped 12- or 24-sided crystals and take a good polish.
Properties
- Chemical formula
- e.g. Fe₃Al₂(SiO₄)₃
- Category
- Silicate
- Hardness (Mohs)
- 6.5–7.5
- Crystal system
- Cubic (isometric)
- Lustre
- Vitreous
- Streak
- White
- Colour
- Red, orange, green, brown
- Cleavage / fracture
- None
How to identify garnet
- →Well-formed many-sided (dodecahedral) crystals, often in schist.
- →Hardness 6.5–7.5: scratches glass, no cleavage.
- →Deep red is most common; also orange, green and brown.
- →Glassy lustre; white streak.
Where garnet is found
Garnet is worldwide in metamorphic rocks, with gem material from Sri Lanka, Madagascar, Tanzania and the USA.
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