Tegengrenite is a rare manganese-magnesium oxide belonging to the spinel group. It is primarily found as tiny, metallic, black grains within manganese-rich metamorphic rocks, most notably at the famous Långban locality in Sweden.

Hardness

Mohs

Luster

Sub-adamantine

Transparency

Translucent

mineralrareSpinel Group family

Tegengrenite

Hardness: 6
Luster: Sub-adamantine
Transparency: Translucent

Is this tegengrenite?

4-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch tegengrenite with a known reference. Tegengrenite sits at Mohs 6, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: sub-adamantine.
3
Match the color range
Compare against the expected color range: dark red.
4
Look at form & habit
Crystal system: trigonal. Typical habit: euhedral crystals, subhedral crystals.

Often confused with

Tegengrenite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Magnetite

Mohs 5.5-6.5

How to tell apart: Luster reads sub-adamantine on Tegengrenite and metallic to submetallic, may be dull on Magnetite.

How to tell apart: Luster reads sub-adamantine on Tegengrenite and submetallic on Hausmannite.

Compare →

Often found alongside tegengrenite

Minerals reported to co-occur with tegengrenite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Mg(Mn,Sb)₂O₄
Mohs hardness: 6
Density: 4.58 g/cm³
Colors: Dark red
Luster: Sub-adamantine
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Euhedral crystals, subhedral crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In a Långban-type Fe-Mn deposit

Where rockhounds find tegengrenite

Classic worldwide localities

Jakobsberg, Filipstad district, Värmland, Sweden

Field-hunting tip

Where it forms: In a Långban-type Fe-Mn deposit. If you start seeing hausmannite, calcite, brucite in float, you are in the right ground. Typical habit: euhedral crystals, subhedral crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tegengrenite?+

Mohs hardness is 6. Luster: sub-adamantine. Common colors include dark red.

Where is tegengrenite found?+

Notable localities include Jakobsberg, Filipstad district, Värmland, Sweden.

Is tegengrenite safe to handle?+

Tegengrenite contains antimony. Wash your hands afterwards, never grind or breathe the dust, and store it apart from specimens you handle often.

What rocks look like tegengrenite?+

Tegengrenite is most often confused with Magnetite, Hausmannite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with tegengrenite?+

Tegengrenite commonly co-occurs with Hausmannite, Calcite, Brucite, Dolomite, Clinohumite, Kinoshitalite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tegengrenite form in?+

Where it forms: In a Långban-type Fe-Mn deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tegengrenite used for?+

Tegengrenite is used in collector.

Find tegengrenite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.