GarnetsThe Garnet Group

Data common to all garnets:

Fracture: Conchoidal, splintery, brittle

Colour or streak: White

Transparency: Transparent to opaque

Mohs' hardness: 6V2-IV2

Double refraction: Normally none

Cleavage: Indistinct

Pleochroism: Absent

Crystal system: (Cubic) rhombic

Fluroescence: Mostly none dodecahedron, icositetrahedron

Luster: Vitreous

  This is a group of differently colored minerals with similar crystal structure and related chemical composition. The main representatives are pyrope, almandite and spessartite (pyralspite series), grossularite, andradite, and uvarovite (ugrandite series). Within the series are also mixed members. The name derives from the Latin for grain because of the rounded crystals and similarity to the red kernals of the pomegranate. Garnet, in the popular sense, is usually understood only as the red "carbuncle stones" pyrope and almandite.

Pyrope Colour: Red, frequently with brown tint Density: 3.62-3.87 Chemical composition: Mg3AI2(Si04)3 magnesium aluminium silicate Refractive index: 1.720-1.756 Dispersion: 0.022 (0.013-0.016) Absorption: 687, 685, 671, 650, 620-520, 505 Pyrope (Greek—fiery) was the fashion stone of the 18th and 19th centuries, especially the "Bohemian Garnet." Deposits are found in Burma (Myanmar), China, Madagascar, Sri Lanka, South Africa, Tanzania, and the United States. Can be confused with almandite, ruby, spinel, and tourmaline. Imitations are made with red glass.

Rhodolite  Purplish red or rose-color garnet between pyrope and almandite in composition.

Almandite Color: Red with violet tint Density: 3.93-4.30 Chemical composition: aluminium silicate Garnet Group Refractive index: 1.770-1.820 Dispersion: 0.027 (0.013-0.016) Absorption: 617, 576, 526, 505, 476, 462, 438, 428, 404, 393

Its name is derived from the town in Asia Minor. Deposits are found in Brazil, India, Madagascar, Sri Lanka, and the United States, as well as the Czech Republic and Austria. Can be confused with pyrope, ruby, spinel, and tourmaline.

Spessartite  Garnet Group Colour: Orange to red-brown Transparency: Transparent, translucent Density: 4.12-4.18 Refractive index: 1.790-1.820 Chemical composition: Mn3AI2(Si04)3 Dispersion: 0.027 (0.015) manganese aluminum silicate Absorption: 495, 485, 462, 432, 424, 412

Its name is derived from occurrence in the Spessart (= forest), Germany. Deposits are found in Burma (Myanmar), Brazil, China, Kenya, Madagascar, Sri Lanka, Tanzania, and the United States. The best specimens come from Namibia ("Mandarin Spessartite"). Can be confused with andalusite, chrysoberyl, fire opal, hes- sonite, sphene, and topaz.