Shigaite is a rare hydrated sulfate mineral that typically forms vibrant, honey-yellow hexagonal plates or rosettes. It is most famous among collectors for specimens found in the manganese mines of Japan and the rare mineral-rich alkaline rocks of Mont Saint-Hilaire, Canada. Collectors should handle these specimens with care, as the mineral is prone to dehydration and damage due to its high water content.
Is this shigaite?
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 shigaite with a known reference. Shigaite sits at Mohs ~2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: very pale yellow to white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to dull.
- 4Match the color rangeCompare against the expected color range: light yellow, orange.
- 5Look at form & habitCrystal system: trigonal. Typical habit: hexagonal, tabular.
Often confused with
Shigaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Shigaite leaves very pale yellow to white, Woodwardite leaves light blue; luster reads vitreous to dull on Shigaite and pearly on Woodwardite.
How to tell apart: Streak differs, so Shigaite leaves very pale yellow to white, Hydrotalcite leaves white; luster reads vitreous to dull on Shigaite and satiny to greasy or waxy on Hydrotalcite.
Often found alongside shigaite
Minerals reported to co-occur with shigaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn₆Al₃(OH)₁₈[Na(H₂O)₆](SO₄)₂·6H₂O
- Mohs hardness
- ~2
- Density
- 2.32 g/cm³
- Colors
- Streak
- Very pale yellow to white
- Luster
- Vitreous to dull
- Transparency
- Semitransparent
- Crystal system
- Trigonal
- Crystal habit
- Hexagonal, tabular
- Cleavage
- On {0001}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in metamorphosed manganese ore deposits
Where rockhounds find shigaite
Classic worldwide localities
- Bengal Cannon mine, Iron Co., Michigan, USA
- Ioi mine, about 25 km east of Kyoto, Shiga Prefecture, Japan
- N’Chwaning mine, and Wessels mine, near Kuruman, Cape Province, South Africa
- Iron Monarch quarry, Iron Knob, South Australia
Field-hunting tip
Where it forms: A rare secondary mineral in metamorphosed manganese ore deposits. If you start seeing rhodochrosite, sonolite, manganosite in float, you are in the right ground. Typical habit: hexagonal, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find shigaite on the map
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