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Manganotantalite  (Tantanlite-Mn)
Current inventory:  0 gems
 

Chemistry:  (Mn²⁺, Fe²⁺)(Ta, Nb)₂O₆  [Iron Manganese Tantalum Niobium Oxide]

Discovered in 1887;   IMA status: Valid (pre-IMA; Grandfathered).
Manganotantalite is named after its chemical composition containing manganese and tantalum. Tantalum is named after the Greek mythical Tantalus, for the difficulty in bringing the mineral into solution.

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.18-40

Nickel-Strunz 10th Ed. ID:

4.DB.35

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
B : With medium-sized cations; chains of edge-sharing octahedra

Related to:

Manganocolumbite-Manganotantalite Series. Ferrotantalite-Manganotantalite Series. Dimorphous with Manganotapiolite.

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Crystals short prismatic or equant, also tabular; in groups of parallel or subparallel crystals; massive (by analogy to Ferrocolumbite).

Twinning:

On [021] and [023], may produce pseudohexagonal trillings

Physical Properties

Cleavage:

[100] Distinct, [010] less Distinct

Fracture:

Sub-Conchoidal to Irregular/Uneven

Tenacity:

Brittle

Hardness (Mohs):

6.0

Density:

6.65 - 8.00 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Pink to nearly Colorless, Redish Brown to Black

Transparency:

Opaque to Translucent

Luster:

Vitreous, Sub-Metallic

Refractive Index:

2.14 - 2.34  Biaxial ( + )

Birefringence:

0.080 - 0.200

Dispersion:

Strong; r < v

Pleochroism:

Strong; X = red, Y = red brown, Z = orange

Occurances

Geological Setting:

As an accessory and primary constituent of granite pegmatites; detrital in placers.

Common Associations:

Albite, Amblygonite, Apatite, Beryl, Cassiterite, Lepidolite, Lithiophilite, Microcline, Microlite, Muscovite, Samarskite, Spodumene, Tourmaline, Triphylite, Triplite

Type Locality:

Utö Island, Haninge, Södermanland, Sweden

Year Discovered:

1887

View mineral photos:

Manganotantalite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Manganotantalite is a mineral with very high density so even small gems are relatively heavy. It also has high dispersion and makes for a beautiful gem when properly cut although gems are usually just translucent. Gems are very rare and difficult to cut because of the cleavage.

The main sources of gemmy to semi-gemmy crystals are Konar Province, Afghanistan; Alto do Giz pegmatite, Rio Grande do Norte, Northeast Region, Brazil; Murrua, Alto Ligonha District, Zambezia Province, Mozambique; and Mbarara District, Uganda.
 

  
Manganotantalite gems for sale:

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