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 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.