Centennialite is a very rare calcium-copper silicate mineral discovered in the mine dumps of the Centennial Mine in Michigan. It typically occurs as small, delicate, colorless to white platy crystals associated with native copper and other secondary minerals in basaltic voids.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Centennialite

Hardness: 2
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this centennialite?

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 centennialite with a known reference. Centennialite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Centennialite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Centennialite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: platy crystals, radial aggregates.

Often confused with

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

mineral

Calcite

Mohs 3

How to tell apart: Calcite is the harder of the two (Mohs 3 vs. 2).

Often found alongside centennialite

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

All properties

Chemical formula: Ca₁₂Cu₄(Si₂O₇)₄Cl₁₂·44H₂O
Mohs hardness: 2
Density: 2.44 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Platy Crystals, Radial Aggregates
Cleavage: Perfect in One Direction
Rarity: Rare
Uses: Collector
Host rock: Basaltic Copper Deposits
Typical price: $50-500 for micro-specimens

Where rockhounds find centennialite

Classic worldwide localities

Centennial Mine, Michigan, USA

Field-hunting tip

Look in basaltic copper deposits country — that is the host setting where centennialite typically forms. If you start seeing cuprite, copper, tenorite in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify centennialite?+

Mohs hardness is 2. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is centennialite found?+

Notable localities include Centennial Mine, Michigan, USA.

How much is centennialite worth?+

Typical asking prices fall in the range of $50-500 for micro-specimens. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like centennialite?+

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

What minerals are found with centennialite?+

Centennialite commonly co-occurs with cuprite, copper, tenorite, chlorite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does centennialite form in?+

Centennialite typically forms in basaltic copper deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is centennialite used for?+

Centennialite is used in collector.

Find centennialite on the map

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