Rock Identifier
Garnet (Red Garnet) (Garnet Group. The red varieties seen in jewelry are typically Almandine (Fe3Al2(SiO4)3), Pyrope (Mg3Al2(SiO4)3), or a mix of the two (pyrope-almandine series).) — Mineral (specifically, a variety of the mineral species Pyrope-Almandine Garnet)
Mineral (specifically, a variety of the mineral species Pyrope-Almandine Garnet)

Garnet (Red Garnet)

Garnet Group. The red varieties seen in jewelry are typically Almandine (Fe3Al2(SiO4)3), Pyrope (Mg3Al2(SiO4)3), or a mix of the two (pyrope-almandine series).

Hardness: 6.5-7.5 on Mohs scale; Color: Deep red, reddish-brown, purplish-red; Luster: Vitreous (glassy) to sub-adamantine; Crystal structure: Isometric (dodecahedral or trapezohedral crystals are common); Cleavage: None (has conchoidal to uneven fracture); Specific Gravity: 3.58-4.32

Hardness
6
Color
Deep red, reddish-brown, purplish-red
Luster
Vitreous (glassy) to sub-adamantine

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Physical properties

Hardness: 6.5-7.5 on Mohs scale; Color: Deep red, reddish-brown, purplish-red; Luster: Vitreous (glassy) to sub-adamantine; Crystal structure: Isometric (dodecahedral or trapezohedral crystals are common); Cleavage: None (has conchoidal to uneven fracture); Specific Gravity: 3.58-4.32

Formation & geological history

Garnets form under a wide range of temperature and pressure conditions in metamorphic, igneous, and sedimentary rocks. Red garnets (almandine and pyrope varieties) are typically found in high-grade metamorphic rocks like schist and gneiss, or in igneous rocks like peridotite and granite. They can also be found in alluvial deposits due to their hardness and resistance to weathering. Geological age varies widely depending on the host rock formation, ranging from Precambrian to Cenozoic.

Uses & applications

Primarily used as a gemstone in jewelry, especially the deep red varieties like almandine and pyrope. Lower quality or industrial-grade garnet is crushed and used as an abrasive in sandpaper, waterjet cutting, and sandblasting. It's also used in water filtration media.

Geological facts

Garnets have been used since the Bronze Age as gemstones and abrasives. Historically, red garnets were thought to be dried drops of blood or solidified fire. Bohemia (now part of the Czech Republic) was a major source of beautiful red garnets for centuries. It's the birthstone for January.

Field identification & locations

In the field, red garnets can often be identified by their characteristic dodecahedral or trapezohedral crystal forms, their deep red color, and their hardness (they can scratch glass). They are commonly found in metamorphic terrains worldwide, with significant deposits in India, Sri Lanka, Brazil, USA (Idaho, Arizona, North Carolina), South Africa, and Bohemia (Czech Republic). Collectors value well-formed crystals and clear, richly colored gem-quality specimens.