Garnet Group: Spessartite & Mandarin Garnet
Spessartite (Spessartine)
Source: Australia, Brazil, Burma, Madagascar, Mozambique, Namibia, Nigeria, Sri Lanka, Tanzania, USA
Spessartite garnet, also known as spessartine, was named for its original location of discovery in the Spessart mountains of northwestern Bavaria in 1832. Spessartine is classified as a nesosilicate manganese aluminium garnet, in the silicate mineral group.
The "garnet group" is divided into six common varieties that are identified by their chemical composition and/or distinct color. The six main garnet types are almandine, andradite, grossularite, pyrope, spessartite, and uvarovite.
Spessartite Composition & Geology
Spessartine commonly occurs within metamorphic rock, and in ultramafic igneous rock formations, granite pegmatite, and low-grade metamorphic phyllites. The major sources for gem-grade orange spessartine are Brazil and Sri Lanka, with a violet-red variety occurring in the USA (Colorado).
Spessartite was also mined in East Africa at Archer's Post, Kenya in the early 1900s, and more recently in Tanzania's Umba River Valley near the Kenya-Tanzania border, in northern Mozambique, and near the Serengeti National Park in northern Tanzania.
Mandarin Garnet
Mandarin Garnet is an extremely rare variety of garnet, and very recent mineral discovery, having been first identified in 1991. Mandarin Garnet, also known as Kunene spessartines, is a manganese (Mn) aluminium (Al) variety of garnet with an intense, and deeply saturated ideochromatic hue of pure-orange to yellowish-orange (above, right).
Since its discovery, the primary source for Mandarin Garnet has been the alluvial secondary deposits along the Kunene River between Namibia and Angola, in southwestern Africa. In recent years this primary source appears to be mined out, and new sources for Mandarin Garnet have been identified in south-western Nigeria in 1994, and more recently in Madagascar and Sri Lanka.
Spessartite specimens from Nigeria have a more reddish-orange hue, while the specimens from Madagascar and Sri Lanka are more of an orange-red with brownish overtones.
Spessartite Garnet & Tsavorite Chemistry, Physical Properties
Spessartite (Mandarin) Garnet & Tsavorite Optical Properties
Bibliography on Spessartine & Mandarin Garnet
Swala Gem Traders, Spessartite Discovery in Northern Tanzania  . www.swalagemtraders.com
ICA, Mandarin Garnet . www.gemstone.org
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