Quantcast

The Mineral spessartine

Perfect Spessartine Crystal on Matrix

Spessartine is member of the Garnet group, and is known for its aesthetic orange and reddish-orange colors. This form of Garnet was once much rarer, but new abundant finds in Tanzania, China, and Pakistan have really put Spessartine on the map, making it very well regarded. Spessartine forms a solid solution series with Almandine, and can be virtually indistinguishable from it in localities where both these Garnets occur together. Spessartine is named after the Spessart Mountains, in Bavaria, Germany, which is the type locality for this mineral.

Chemical Formula

Mn3Al2Si3O12

Color

Orange, brown, brownish-red, red, dark red, pink, yellowish-brown, yellow, gray, black. Sometimes multicolored red and black.

Crystal System

Isometric

Properties

Streak
Colorless
Hardness
7
Transparency
Transparent to translucent
Specific Gravity
4.2
Luster
Vitreous
Cleavage
None
Fracture
Conchoidal to uneven
Tenacity
Brittle

Crystal Habits

Occurs in single trapezohedral crystals, often well developed. Less often in dodecahedral crystals or in trapezohedral-dodecahedral combinations. Also in dense crystal clusters, in grainy aggregates, drusymassive, and in veins in host rock. Crystals are occasionally striated and are sometimes in heavily etched complex forms.

3D Crystal Atlas

Additional Information

Composition
Manganese aluminum silicate. The manganese is often replaced by some magnesium and iron.
In Group
Silicates; Nesosilicates; Garnet Group
Striking Features
Color, crystal forms, and hardness
Environment
In igneous rocks in granite pegmatites, and in contact and regional metamorphic schists and hornfels.
Rock Type
Igneous, Metamorphic

Other Names

Spessartite

Varieties

 -   Gemstone trade name for a reddish-orange form of Spessartine Garnet (or a more accurately a mixture intermediary between Spessartine and Pyrope) that originates in the Umba River Valley in Tanzania and Kenya. This term is sometimes also used as a synonym for Spessartine. Although this is a relatively new term, it has become accepted in the gem trade.

Uses

Transparent Spessartine can be faceted as a gemstone and used in jewelry. It is the most widely used orange and reddish-orange Garnet. Spessartine specimens, especially those recently found in Tanzania, are very popular among mineral collectors.
Also see the gemstone section on Spessartite and Garnet.

Noteworthy Localities

A new outstanding occurrence of bright orange Spessartine crystals in Tanzania was first brought to the market in 2008. The deposit is in Nani, Loliondo, Arusha Region, near the Serengeti National Park. Bright orange crystals once came from Marienfluss, Kunene Region, Namibia, but these high quality Spessartine forms are very hard to come across today. Another important African locality is the Jos Plateu, Nigeria. Malaya Garnet (a trade name for Garnet intermediary between Spessartine and Pyrope) is well-known from Mwakaijembe in the Umba River Valley, Tanzania.

Another recent outstanding discovery of Spessartine was in China, where it first discovered in the late 1990's in Tongbei and Yunling, Zhangzhou Prefecture. The Chinese Spessartine is often in dense aggregates of small gemmy crystals coating Smoky Quartz. The finest dark red Spessartine, usually associated with contrasting white Albite, comes from Pakistan at Shengus and the Shigar Valley, Skardu District; and in the Gilgit District. Spessartine of similar quality is also found in Darra-i-Pech, Nangarhar Province, Afghanistan.

Lustrous Spessartine, sometimes in complex crystals with deep etchings, comes from several of the gem pegmatite in Minas Gerais, Brazil, especially at Conselheiro Pena, São José da Safira, and Galiléia, all in the Doce valley. Especially noted is the Navegadora Mine in São José da Safira which produces heavily etched contorted crystals. Other worldwide Spessartine occurrences include Broken Hill, New South Wales, Australia; Val Codera, Sondrio, Italy; San Piero in Campo, Elba Island, Italy; and Iveland, Aust-Agder, Norway.

In the U.S., the most well-known occurrences of Spessartine are the Little Three Mine, Ramona, San Diego Co., California; the Pack Rat Mine, Jacumba, San Diego Co., California; Ruby Mountain, Nathrop, Chaffee Co., Colorado; East Grants Ridge, Cibola Co., New Mexico; and the Thomas Range, Juab Co., Utah.

Distingushing Similar Minerals

Pyrope - Color is usually deeper red.
Grossular - Very hard to distinguish without complex methods, although Grossular crystals are rarely trapezohedral, whereas Spessartine is more often trapezohedral.
Andradite - Very hard to distinguish without complex methods.


Close

Copyright © 2021. Minerals.net

View on Full Site