Orange Garnet

Spessartine occurs in granite pegmatites and also in gneiss, quartzite, rhyolite and some skarns. IGS lists Namibia, Nigeria and Tanzania as major sources of spessartine, including mandarin garnet, with other gem sources in Brazil, the gem gravels of Sri Lanka and Myanmar, and the United States (Ramona, California; Amelia, Virginia). Orange and brown grossular (hessonite) comes from the gem gravels of Sri Lanka, Harts Range in Australia and the Jeffrey Mine in Quebec, Canada.

Refractive index and specific gravity separate the two main types: spessartine (RI 1.79–1.83) is higher than grossular (1.720–1.800), and spessartine shows a manganese absorption spectrum with strong lines at 4320 and 4120 Å. Most orange spessartines have eye-visible inclusions such as wavy feathers, while grossular often shows a swirled, granular "treacle" look under magnification. There are no known treatments for spessartine. Orange yttrium aluminum garnet (YAG), colored cubic zirconia and synthetic corundum have been sold as "synthetic spessartite", and lab-grown corundum has even been sold as natural spessartite rough.

GIA notes that garnets are stable to light and chemicals but can be attacked by hydrofluoric acid; they have fair to good toughness and should be protected from hard blows. Warm, soapy water is always safe, an ultrasonic cleaner is usually safe except for fractured stones, and steam cleaning is not recommended. Garnets might rarely be fracture-filled; such stones should be cleaned only with warm, soapy water. IGS adds that because spessartines tend to contain inclusions and grossulars have some heat sensitivity, mechanical cleaning systems and extreme heat are best avoided; use warm water, mild detergent and a soft brush.

Spessartine is named after its type locality, the Spessart Mountains in Bavaria, Germany. Before mandarin garnets were discovered in the 1990s, bright orangish red spessartines from Ramona, California, and Amelia County, Virginia, were the most valuable. The name hessonite comes from the Greek "hesson", "inferior", referring to its lower hardness and density than most other garnets; older names for it include cinnamon stone.

Garnet is the birthstone for January and the gem of the second wedding anniversary.