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.
Is this shimazakiite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch shimazakiite with a known reference. Shimazakiite sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: grayish white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, aggregates.
Often confused with
Shimazakiite vs. its common look-alikes, and how to tell them apart in the field.
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
- 4.5
- Density
- 2.81 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In an irregular vein in crystalline limestone near gehlenite-spurrite-bearing contact metamorphic rocks (skarn)
Where rockhounds find shimazakiite
Classic worldwide localities
- Fuka mine, Okayama Prefecture, Japan
Field-hunting tip
Where it forms: In an irregular vein in crystalline limestone near gehlenite-spurrite-bearing contact metamorphic rocks (skarn). If you start seeing takedaite, sibirskite, olshanskyite in float, you are in the right ground. Typical habit: tabular crystals, aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify shimazakiite?+
Where is shimazakiite found?+
What rocks look like shimazakiite?+
What minerals are found with shimazakiite?+
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What is shimazakiite used for?+
Find shimazakiite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
