Ferrocolumbite

Ferrocolumbite, also called niobite, columbate and columbite [(Fe, Mn)(Nb, Ta)2O6] is a black mineral that is an ore of niobium and tantalum. It has a submetallic luster and a high specific gravity and is a niobate of iron and manganese, containing tantalate of iron. This mineral was first found at Haddam, Middlesex County, Connecticut in New England, USA. It forms a series with the tantalum-dominant analogue Ferrotantalite and one with the manganese-dominant analogue Manganocolumbite.
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General Information:
 Chemical Formula:
Fe++Nb2O6
 Composition:
(Molecular Weight = 337.66 gm)
Niobium 55.03 % Nb
Iron 16.54 % Fe
Oxygen 28.43 % O 
 Empirical Formula:
Fe2+Nb2O6
 Environment:
Pegmatites, and alluvial deposits.
 Locality:
M'buye Mine, Rwanda.
 Name Origin:
Named after its content of the element niobium, formerly called columbium and the Latin ferrium - "iron."
Physical Properties:
 Cleavage:
[010] Distinct
 Color:
black or brownish black.
 Density:
5.3 - 7.3, Average = 6.3
 Diaphaniety:
Translucent to opaque
 Habits:
Massive - Granular - Common texture observed in granite and other igneous rock., Striated - Parallel lines on crystal surface or cleavage face.,
 Hardness:
6 - Orthoclase
 Luminescence:
Non-fluorescent.
 Luster:
Sub Metallic
 Streak:
blackish brown
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