Hydrogrossular Garnet Value, Price, and Jewelry Information

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Hydrogrossular garnet cabochon, 24.43 cts, 33.6 x 16 mm, Peru. © The Gem Trader. Used with permission.

Hydrogrossular Garnet

Hydrogrossular differs from the other garnets in that it is never transparent. It ranges from translucent to opaque. The most common color is a bluish green, but they are also found in pink, white, and gray.

Hydrogrossular Garnet Information

Data	Value
Name	Hydrogrossular Garnet
Is a Variety of	Grossular Garnet
Heat Sensitivity	Some
Formula	Ca₃Al₂(SiO₄)_3-x(OH)_4x
Colors	Bluish green, green, pink, white, gray
Fracture	Conchoidal, splintery
Hardness	6.5-7.5
Cleavage	None
Crystallography	Isometric
Refractive Index	1.72-1.80
Birefringence	None
Dispersion	0.028
Pleochroism	None.
Optics	Isotropic
Luster	Waxy
Specific Gravity	3.40-3.70
Transparency	Translucent to opaque
Birthstone	January

Because of its coloring and translucency, hydrogrossular is often used as a jade substitute. Large pieces are available, which lend themselves to carving.

Material from New Zealand is known as rodingite (N = 1.702, specific gravity 3.35). So-called Transvaal jade from South Africa occurs in green, gray-green, blueish, and pink colors. Compact and homogeneous, it may have a splintery fracture and waxy luster. The gray material contains zoisite. Pink material, containing Mn, has N = 1.675-1.705 and specific gravity of 3.27. The green, jade-like material has N = 1.728 and specific gravity 3.488.