Steacyite is a rare thorium-bearing silicate mineral found in alkaline pegmatites and igneous complexes. Collectors prize it primarily for its distinct crystal habits and its association with other rare minerals at localities like Mont Saint-Hilaire.
Is this steacyite?
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 steacyite with a known reference. Steacyite sits at Mohs 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: brown, yellow green.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: massive, radial.
Often confused with
Steacyite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside steacyite
Minerals reported to co-occur with steacyite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KTh(Ca,Na)₂Si₈O₂₀
- Mohs hardness
- 5
- Density
- 2.95 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent to transparent in thin section
- Crystal system
- Tetragonal
- Crystal habit
- Massive, radial
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In cavities in pegmatite veins in nepheline syenite in an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada); in a miarolitic cavity in nepheline syenite (Rouma Isle, Guinea)
Where rockhounds find steacyite
Classic worldwide localities
- Mont Saint-Hilaire, Quebec, Canada
- Rouma Isle, Los Islands, Guinea
- Dara-i-Pioz massif, Alai Range, Tien Shan, Tajikistan
Field-hunting tip
Where it forms: In cavities in pegmatite veins in nepheline syenite in an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada); in a miarolitic cavity in nepheline syenite (Rouma Isle, Guinea). If you start seeing nenadkevichite, analcime, aegirine in float, you are in the right ground. Typical habit: massive, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify steacyite?+
Where is steacyite found?+
Is steacyite safe to handle?+
What rocks look like steacyite?+
What minerals are found with steacyite?+
What kind of rock does steacyite form in?+
What is steacyite used for?+
Find steacyite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
