Thermaerogenite is a rare copper-aluminum oxide belonging to the spinel group, typically formed in volcanic fumarole environments. It usually appears as small, dark octahedral crystals deposited from volcanic gases.

Hardness

7.5-8

Mohs

Luster

Vitreous

Streak

White

Transparency

Opaque

mineralrareSpinel Group family

Thermaerogenite

Hardness: 7.5-8
Luster: Vitreous
Streak: White
Transparency: Opaque

Is this thermaerogenite?

5-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 thermaerogenite with a known reference. Thermaerogenite sits at Mohs 7.5-8 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Thermaerogenite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Thermaerogenite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: dark green, black.
5
Look at form & habit
Crystal system: cubic. Typical habit: octahedral.

Often confused with

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

How to tell apart: Streak differs — Thermaerogenite leaves white, Gahnite leaves gray.

Compare →

All properties

Chemical formula: CuAl₂O₄
Mohs hardness: 7.5-8
Density: 4.45 g/cm³
Colors: Dark Green Black
Streak: White
Luster: Vitreous
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Octahedral
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Fumarolic Encrustations
Typical price: $100-500+ per specimen

Where rockhounds find thermaerogenite

Classic worldwide localities

Vesuvius (Italy)

Field-hunting tip

Look in fumarolic encrustations country — that is the host setting where thermaerogenite typically forms. If you start seeing copper minerals, aluminosilicates in float, you are in the right ground. Field specimens usually show a octahedral habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify thermaerogenite?+

Mohs hardness is 7.5-8. It typically shows a vitreous luster. The streak is white. Common colors include dark green, black.

Where is thermaerogenite found?+

Notable localities include Vesuvius (Italy).

How much is thermaerogenite worth?+

Typical asking prices fall in the range of $100-500+ per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like thermaerogenite?+

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

What minerals are found with thermaerogenite?+

Thermaerogenite commonly co-occurs with Copper minerals, Aluminosilicates. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does thermaerogenite form in?+

Thermaerogenite typically forms in fumarolic encrustations. Working float back to the host body is the standard way to chase a fresh occurrence.

What is thermaerogenite used for?+

Thermaerogenite is used in collector.

Find thermaerogenite on the map

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