Grossmanite is an extremely rare titanium-rich pyroxene found almost exclusively in calcium-aluminum-rich inclusions within carbonaceous chondrite meteorites. It appears as dark green to black massive grains and is highly sought after by meteorite collectors and mineralogists studying the early formation of the solar system.

Hardness

6-7

Mohs

Transparency

Transparent

mineralrarePyroxene Group family

Grossmanite

Hardness: 6-7
Transparency: Transparent

No image

Is this grossmanite?

3-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 grossmanite with a known reference. Grossmanite sits at Mohs 6-7, softer than the next harder reference, harder than the previous one.
2
Match the color range
Compare against the expected color range: dark green, black.
3
Look at form & habit
Crystal system: monoclinic. Typical habit: massive.

Often confused with

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

Often found alongside grossmanite

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

All properties

Chemical formula: Ca(Ti,Mg,Ti)AlSiO₆
Mohs hardness: 6-7
Density: 3.41 g/cm³
Colors: Dark green Black
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Massive
Rarity: Rare
Uses: Collector, Research
Host rock: Likely formed through high-temperature condensation in the solar nebula, followed by melting and crystallization in Ca-,Al-rich refractory inclusions in a meteorite

Where rockhounds find grossmanite

Classic worldwide localities

Allende meteorite (type locality)

Field-hunting tip

Where it forms: Likely formed through high-temperature condensation in the solar nebula, followed by melting and crystallization in Ca-,Al-rich refractory inclusions in a meteorite. If you start seeing spinel, perovskite, grossite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify grossmanite?+

Mohs hardness is 6-7. Common colors include dark green, black.

Where is grossmanite found?+

Notable localities include Allende meteorite (type locality).

What rocks look like grossmanite?+

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

What minerals are found with grossmanite?+

Grossmanite commonly co-occurs with Spinel, Perovskite, Grossite, Melilite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does grossmanite form in?+

Where it forms: Likely formed through high-temperature condensation in the solar nebula, followed by melting and crystallization in Ca-,Al-rich refractory inclusions in a meteorite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is grossmanite used for?+

Grossmanite is used in collector, research.

Find grossmanite on the map

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