Numanoite is an extremely rare copper-bearing borosilicate mineral first discovered in Japan. It typically occurs as small tabular crystals within skarn deposits and is highly prized by advanced mineral collectors for its unique chemistry.

Hardness

5-5.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareDatolite Group family

Numanoite

Hardness: 5-5.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this numanoite?

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 numanoite with a known reference. Numanoite sits at Mohs 5-5.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Numanoite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Numanoite 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: tabular crystals.

Often confused with

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

How to tell apart: Gadolinite-(Y) is the harder of the two (Mohs 6.5-7 vs. 5-5.5).

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Often found alongside numanoite

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

All properties

Chemical formula: Ca₂Cu(BO₃)(SiO₄)(OH)
Mohs hardness: 5-5.5
Density: 3.37 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Tabular Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Skarn
Typical price: $50-300 for small specimens

Where rockhounds find numanoite

Classic worldwide localities

Numano mine, Okayama Prefecture, Japan

Field-hunting tip

Look in skarn country — that is the host setting where numanoite typically forms. If you start seeing diopside, quartz, calcite in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify numanoite?+

Mohs hardness is 5-5.5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is numanoite found?+

Notable localities include Numano mine, Okayama Prefecture, Japan.

How much is numanoite worth?+

Typical asking prices fall in the range of $50-300 for small specimens. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like numanoite?+

Numanoite is most often confused with Datolite, Gadolinite-(Y). A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with numanoite?+

Numanoite commonly co-occurs with Diopside, Quartz, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does numanoite form in?+

Numanoite typically forms in skarn. Working float back to the host body is the standard way to chase a fresh occurrence.

What is numanoite used for?+

Numanoite is used in collector.

Find numanoite on the map

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