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, so Thermaerogenite leaves white, Gahnite leaves gray.

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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, 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

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