Shimazakiite is a rare calcium borate mineral that typically forms in contact metamorphic skarns. It is primarily known from its type locality at the Fuka mine in Japan, where it occurs as small, clear to yellowish crystals associated with other calcium-rich silicates.

Hardness

3.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Shimazakiite

Hardness: 3.5
Luster: Vitreous
Streak: White
Transparency: Transparent

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Is this shimazakiite?

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 shimazakiite with a known reference. Shimazakiite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Shimazakiite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Shimazakiite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white, pale yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: tabular crystals, aggregates.

Often confused with

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

mineral

Priceite

Mohs 3-3.5

How to tell apart: Luster reads vitreous on Shimazakiite and dull on Priceite.

How to tell apart: Shimazakiite is noticeably harder (Mohs 3.5 vs. 2).

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Often found alongside shimazakiite

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

All properties

Chemical formula: Ca₂B₂O₅
Mohs hardness: 3.5
Density: 3.16 g/cm³
Colors: Colorless White Pale Yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Tabular Crystals, Aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Skarn Deposits
Typical price: n/a

Where rockhounds find shimazakiite

Classic worldwide localities

Fuka mine, Okayama Prefecture, Japan

Field-hunting tip

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

Common questions

How do you identify shimazakiite?+

Mohs hardness is 3.5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white, pale yellow.

Where is shimazakiite found?+

Notable localities include Fuka mine, Okayama Prefecture, Japan.

How much is shimazakiite worth?+

Typical asking prices fall in the range of n/a. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like shimazakiite?+

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

What minerals are found with shimazakiite?+

Shimazakiite commonly co-occurs with Fukalite, Tilleyite, spurrite, gehlenite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does shimazakiite form in?+

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

What is shimazakiite used for?+

Shimazakiite is used in collector.

Find shimazakiite on the map

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