Rhodolite

Rhodolite
General
Category	Pyrope variety, nesosilicate
Formula (repeating unit)	(Mg,Fe)3Al2(SiO4)3
Crystal system	Cubic
Identification
Color	light to dark purplish red through reddish purple
Cleavage	none, may show indistinct parting
Fracture	conchoidal
Mohs scale hardness	7–7.5
Luster	greasy to vitreous
Specific gravity	3.84 (+/− .10)
Polish luster	vitreous
Optical properties	Single refractive, often anomalous double refractive
Refractive index	1.760 (+.010, −.020)
Birefringence	none
Pleochroism	none
Dispersion	.026
Ultraviolet fluorescence	inert
Absorption spectra	usually at 504, 520, and 573 nm, may also have faint lines at 423, 460, 610, and 680–690 nm
References

Rhodolite is a varietal name for rose-pink to red mineral pyrope, a species in the garnet group. It is found in Cowee Valley, Macon County, North Carolina. The name is derived from the Greek for "rose-like", in common with many pink mineral types (e.g. rhodochrosite, rhodonite). Rhodolite itself is not officially recognized as a mineralogical term. This coloration, and the commonly inclusion-free nature of garnet from this locality, has led to rhodolite being used as a semi-precious gemstone.

Rhodolite garnets appear as transparent red gemstones. The color may vary from a rose-pink, a purple-pink, a purple-red, to a raspberry-red.

Chemically, the rhodolite is a mix of pyrope and almandine garnets, part of the pyrope-almandine solid-solution series, with an approximate garnet composition of Py₇₀Al₃₀.

The color of rhodolites, combined with their brilliance, durability, and the accessibility of stones with no visible inclusions have brought about some demand for the stone in the jewelry industry. Rhodolites used in jewelry are generally faceted to make good use of their brilliance, though they also exist in cabochon form.

Some rhodolites will change color from purplish to a hessonite brown when heated to a temperature of 600 °C. This process cannot be reversed.

Deposits of rhodolite garnet have been found in Brazil, Greenland, Kenya, Madagascar, Mozambique, Norway, Sri Lanka, and the United States.

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