Crystal Magnetite

Chemical Formula

MnO(OH)

Composition

Basic manganese hydroxide

Color

Dark gray to black

Streak

Reddish brown to black

Hardness

3.5 - 4

Crystal System

Monoclinic

Crystal Forms 
and Aggregates

Manganite is best known in aggregates of blocky and short prismatic crystals. Crystal aggregates are usually in disorganized clusters with the crystals coming out of all directions. Thick crystals are heavily striated lengthwise, and often exhibit curvature. Twinning, in both penetration twinning and contact twinning, is known. Additional habits include acicular, radiating, fibrous, plumose, mammilary, globular, grainy, and massive.

Transparency

Opaque

Specific Gravity

4.3 - 4.4

Luster

Submetallic

Cleavage

1,1

Fracture

Uneven

Tenacity

Brittle

In Group

Oxides; Hydroxides

Striking Features

Crystal habit, mode of occurrence, and streak

Environment

In low temperature hydrothermal replacement deposits, acid-rich bogs, and in manganese-rich hot springs.

Rock Type

Sedimentary, Metamorphic

Popularity (1-4)

2

Prevalence (1-3)

2

Demand (1-3)

2