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www.mineralgallery.co.za Minerals A-E |
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Andradite Garnet |
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Name
Andradite Garnet
Chemistry
Ca3Fe2(SiO4)3
Uses
As a specimen
Color
Brown to reddish brown or red
Hardness
6.5-75
Specific gravity
3.7-4.1
Streak
White
Crystals
(Cubic) Rhombododecohedral, icositerahedron; intergrowth; and superficial growth; seldom twinning
Accompanied by:
Beryl, garnet, tourmaline, spinel, phenakite
Similar to:
Grossular, olivine, emerald, idocrase, topaz
Andradite is the lessor cousin of the pyrope and the almandine. The latter two being cut into gems. It is nevertheless an attractive mineral. It has good luster and is found in pegmatites in South Africa in the Kalahari manganese fields together with hematite, hausmannite, barite, celestine, kutnahorite, gaudefroyite and calcite. The Ca-Fe garnet is the most common gangue mineral in high grade ores at the N'Cwaning1 and 2, WESSELS, Hotazel and Black Rock mines. Beautiful wine red and brown-red crystals are found. Keep coming back to this page for more uploads.
Garnets belong to the isometric crystal system and commonly occur in well-formed dodecathedral or trapezohedral crystals. Because of the tight packing of their atoms, garnets are relatively hard and dense.
Natural garnets are divided into the calcium-bearing ugrandites, named after the initial letters of the calcium species uvarovite, grossular and andradite
Calcium-free pyralspites, named after the members pyrope, almandine, and spessartine. Aluminum, iron, and chromium substitute freely in the ugrandites. Iron, magnesium, and manganese substitute readily for one another in the pyralspites, and all gradations between the pure species are possible. Much less substitution occurs between the two groups.
