Formula: Mn2+Nb2O6
Multiple oxide containing niobium and manganese, columbite group, forms series with columbite-(Fe) and with tantalite-(Mn)
Specific gravity: 5.28
Hardness: 6
Streak: Dark red to black
Colour: Black to brownish black, dark red-brown, reddish brown in transmitted light

Placer deposits

Columbite-(Mn) occurs as an accessory and primary constituent of granite pegmatites, or in placers. Associated minerals include albite, microcline, beryl, lepidolite, muscovite, tourmaline, spodumene, lithiophilite, triphylite, amblygonite, triplite, apatite, samarskite, microlite and cassiterite (HOM). The pure end-member is not found in nature, although it has been synthesised (Dana).


The Koktokay No. 3 pegmatite, Altay Mine, Koktokay pegmatite field, Fuyun county, Aletai Prefecture, Yili Hasake Autonomous Prefecture, Xinjiang, China, hosts many minerals including columbite-(Mn) (Extra Lapis Beryl p67).

The Pulsifer pegmatite, West Mount Apatite Mining District, Auburn, Androscoggin county, Maine, USA, is a rare-element granitic pegmatite that intrudes upper amphibolite facies metapelites and biotite schists that are locally interbedded with calc-silicate rocks. The pegmatite exhibits five distinct zonations.
The border zone consists of fine to mediumgrained equi-granular quartz and plagioclase, and minor biotite and almandine.
The wall zone consists of slightly graphic K-feldspar, quartz, biotite and almandine.
The first intermediate zone is characterised by coarse-grained graphic feldspar and plumose muscovite-quartz aggregates. Almandine and schorl are found as accessory minerals, and rare beryl has been observed.
The first intermediate zone grades irregularly into a coarse-grained plagioclase plus quartz plus muscovite second intermediate zone.
The pocket zone assemblage, which lies below the second intermediate zone and immediately above the garnet seam, consists primarily of cleavelandite and quartz, although locally blocky K-feldspar and muscovite are also abundant. Gem tourmaline, beryl, fluorapatite, hydroxylherderite, gahnite, almandine, columbite-(Mn) and cookeite are among the minerals that have been found within the pocket zone.
The garnet seam is a 1 to 5 cm thick layer of 2 mm to 3 cm euhedral almandine plus anhedral smoky quartz.
Just below the garnet seam lies a zone of undetermined thickness that is composed primarily of blocky graphic albite.
Rare columbite-(Mn) is the most prominent niobium-tantalum oxide mineral present (R&M 97.1.8-11).

The Emmons pegmatite, Greenwood, Oxford county, Maine, USA, is situated in a belt of metasedimentary rocks which originated as marine sediments which were subsequently deformed and metamorphosed. It is an example of a highly evolved boron, lithium, cesium and tantalum enriched pegmatite. Columbite-(Mn) crystals with a blocky habit have been noted in the intermediate zone as well as in small miarolitic cavities in the albite replacement units. Some of the crystals also exhibit a striking blue tarnish. Crystals usually range from 1 mm to 2 cm in size. Higher manganese content results in a brown hue, and a blockier habit is usually associated with elevated tantalum content (R&M 94.6.506).

At the Chickering Mine, Walpole, Cheshire county, New Hampshire, USA, columbite-(Mn) microcrystals have been sparingly found embedded in quartz, the largest being 3.5 mm in length. The crystals are black and are well-formed prismatic or flat tabular in habit (R&M 90.415).

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