Crystal Hubnerite

Chemical Formula

MnWO₄

Composition

Manganese tungstate, often with a variable amount of iron
 

Color

Dark red, dark brown, reddish black, black

Streak

Reddish brown to black

Hardness

4 - 4.5

Crystal System

Monoclinic

Crystal Forms 
and Aggregates

Most often in long prismatic crystals, columnar groups, blocky and chisel-shaped crystals, and flattened tabular crystals. Also in dense bladed clusters and rosettes, reticulated, acicular, grainy, and massive. Crystals are often striated lengthwise, and may be twinned as repeated twins with a v-shaped notch in the center.

Transparency

Opaque. Transparent in thin splinters or when backlit.

Specific Gravity

7.1 - 7.3

Luster

Adamantine, submetallic

Cleavage

1,1. May exhibit parting between crystals.

Fracture

Uneven

Tenacity

Brittle

In Group

Tungstates and Molybdates

Striking Features

Heavy weight, color, cleavage, and mode of occurrence.

Environment

In tungsten deposits composed of high and medium temperature hydrothermal Quartz veins; also in granite pegmatites.
 

Rock Type

Igneous, Metamorphic

Popularity (1-4)

2

Prevalence (1-3)

3

Demand (1-3)

1