 ORDER |
|
|
|
Garnet (various calcium and aluminum silicates)
Color: Red, brown, orange, yellow, green, blue, violet, colorless and black.
Cleavage: Imperfect
Fracture: Subconchoidal, usually brittle.
Heat sensitivity: Low to none, but tiny flaws such as cracks and bubbles can be exacerbated with heat. Rhodolite seems to be the most heat sensitive of the garnets.
Pleochroism: None
Birefringence (double refraction): Only in rhodolite.
Crystal structure: Isometric, rhombic, dodecahedron.
--------Pyralspite Subgroup:
Pyrope (magnesium aluminum silicate - occasionally contains chromium and usually some iron colorants.)
Color: Intense deep red.
Moh’s hardness: 7-7.5
Refractive index: 1.73-1.76
Critical angle: 35°
Specific gravity: 3.65-3.8
Dispersion: Moderately high (.022-.023)
Almandite (iron aluminum silicate - iron is the red colorant.)
Color: Deep red with a wine to brown undertone.
Moh’s hardness: 7.5
Refractive index: 1.78-1.83
Critical angle: 34.5°
Specific gravity: 3.95-4.25
Dispersion: Moderately high (.024-.027)
Spessartite (magnesium aluminum silicate - manganese is the orange colorant.)
Color: Orange, red to brown.
Moh’s hardness: 7-7.5
Refractive index: 1.795-1.815
Critical angle: 33.5°
Specific gravity: 4.12-4.2
Dispersion: Moderately high (.027)
Rhodolite (combination of pyrope and almandine - iron is the purple colorant.)
Color: Rose-red, raspberry to violet.
Moh’s hardness: 7-7.5
Refractive index: 1.75-1.77
Critical angle: 34.5°
Specific gravity: 3.95-4.25
Dispersion: Moderately high (.023-.027)
Birefringence (double refraction): None to slight.
--------Ugrandite Subgroup:
Grossular (calcium aluminum silicate)
Types/Color:
Tsavorite - Green - vanadium is the green colorant.
Leuco garnet - Colorless
Hessonite - Brown-orange, peachy-pink - manganese is the orange/yellow colorant.
Moh’s hardness: 7
Refractive index: 1.78-1.83
Critical angle: 34.5°
Specific gravity: 3.95-4.25
Dispersion: Moderately high (.024-.027)
Andradite (calcium iron silicate)
Types/Color:
Demantoid - Green, yellow-green to yellow-brown - chromium and iron are the green colorants.
Topazolite - Lemon-yellow
Melanite - Opaque black
Moh’s hardness: 6.5-7
Refractive index: 1. 85-1.899
Critical angle: 32
Specific gravity: 3.82-3.85
Dispersion: Very strong (.057)
Birefringence (double refraction): None to slight.
Cutting: Pre-polishing with a 1200 Nubond or a 3000 standard lap may cause orange peel which makes polishing difficult.
Polishing: Alumina on most common polishing laps. 50,000 diamond on most polishing laps, and 100,000 on ceramic.
Comments: Garnet does not always form in one of the above types. Many garnets are a mix of different types. For example Mali garnet, is a combination of andradite and grossular. Dematoid (andradite) is the most valuable green garnet, and is extremely rare. Most green garnet is tsavorite (grossular), which is still quite valuable. A recent find of garnet has photochroic (color change) properties.
Catalog Index Specials! Gemstone Properties What's New List Privacy Policy Contact Us
Copyright by ColorWright - All Rights Reserved. Our Privacy Policy. Toll Free Order Line FOR ORDERS ONLY (877) 548-1439 or Email Us