Melanite  (variety of Andradite Garnet)
Current inventory:  0 gems
 

  
Melanite is named from the Greek word "melan", meaning black. Andradite is named for José Bonifácio de Andrada e Silva (1763-1838), Brazilian mineralogist.

Discovery year unknown;   IMA status:  Not Valid (a variety of Andradite Garnet)

Chemistry

Chemical Formula:

Ca₃Fe³⁺₂(SiO₄)₃  + Ti

Calcium Iron Titanium Silicate

Molecular Weight:

508.18 gm (Andradite)

Composition:

Calcium

23.66 %

Ca

33.11 %

CaO

(based on Andradite):

Iron

21.98 %

Fe

28.28 %

FeO

Silicon

16.58 %

Si

35.47 %

SiO₂

Titanium

?? %

Ti

?? %

TiO₂

Oxygen

37.78 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/A.08-110

Nickel-Strunz 10th Ed. ID:

9.AD.25

9 : SILICATES (Germanates)
A : Nesosilicates
D : Nesosilicates without additional anions; cations in [6] and/or greater coordination

Related to:

Variety of Andradite. Garnet Group. Andradite-Grossular Series. Andradite-Schorlomite Series.

Varieties:

None

Synonyms:

Titanian Adradite

Crystal Data

Crystallography:

Isometric - Hexoctahedral

Crystal Habit:

Commonly well-crystallized dodecahedra, trapezohedra, or combinations, to 5 cm. Also granular to massive.

Twinning:

None

Physical Properties

Cleavage:

None

Fracture:

Irregular/Uneven, Conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.5 - 7.0

Density:

3.80 - 3.90 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Black

Transparency:

Opaque

Luster:

Adamantine, Resinous, Dull

Refractive Index:

1.887  Isotropic

Birefringence:

0.000 (Isotropic)

Dispersion:

Andradite: 0.057

Pleochroism:

None

Anisotrophism:

Typically Weak

Occurances

Geological Setting:

In skarns from contact metamorphosed impure limestones or calcic igneous rocks; in chlorite schists and serpentinites; in alkalic igneous rocks, then typically titaniferous.

Common Associations:

Chlorite Group, Vesuvianite, Epidote, Spinel, Calcite, Dolomite, Magnetite

Common Impurities:

Ti, Cr, Al, Mg

Type Locality:

Unknown. Andradite: Drammen, Buskerud, Norway

Year Discovered:

Unknown. Andradite: 1868

View mineral photos:

Melanite Mineral Photos and Locations

More Information

Mindat.org (Melanite)
Mindat.org (Andradite)
Webmineral.com (Andradite)

Melanite is a black, titanium-rich, variety of Andradite Garnet. The Andradite variety of the Garnet Group of minerals includes Melanite (black), Demantoid (green) and Topazolite (yellow). Melanite's black color is due to its high titanium content and is occassionally referred to as "titanian adradite".

Although there are many localities for Melanite, there are three that are known for crystals large enough for faceting: Nioro du Sahel Circle, Kayes Region, Mali; Chihuahua, Mexico; Dallas Gem Mine (Benitoite Mine), Diablo Range, San Benito County, California, USA.
 

  
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