Truscottite is a rare calcium silicate mineral typically found in cavities of igneous rocks or contact metamorphic environments. It is most easily identified by its distinctive pearly luster and platy, often foliated or radiating crystal habit.
Is this truscottite?
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 truscottite with a known reference. Truscottite sits at Mohs 3.5, 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: pearly on the cleavage.
- 4Match the color rangeCompare against the expected color range: white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: aggregates, micaceous, spherical.
Often confused with
Truscottite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads pearly on the cleavage on Truscottite and vitreous to pearly on Gyrolite.
How to tell apart: Okenite is the harder of the two (Mohs 5 vs. 3.5); luster reads pearly on the cleavage on Truscottite and vitreous to pearly on Okenite.
How to tell apart: Prehnite is the harder of the two (Mohs 6-6.5 vs. 3.5); luster reads pearly on the cleavage on Truscottite and vitreous, weak pearly on {001} on Prehnite.
Often found alongside truscottite
Minerals reported to co-occur with truscottite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₁₄Si₂₄O₅₈(OH)₈·2H₂O
- Mohs hardness
- 3.5
- Density
- 2.47-2.48 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly on the cleavage
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
- Crystal habit
- Aggregates, micaceous, spherical
- Cleavage
- Perfect on {0001}, micaceous
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In epithermal gold-silver quartz veins cutting altered pyroclastics (Toi mine, Japan)
Where rockhounds find truscottite
Classic worldwide localities
- Kilauea volcano, Hawaii, and from Yellowstone National Park, Wyoming, USA
- Lebong Donok Au-Ag mine, Benkulen, Sumatra, Indonesia
- Toi mine, Shizuoka Prefecture, Japan
- Hatrurim Formation, Israel
Field-hunting tip
Where it forms: In epithermal gold-silver quartz veins cutting altered pyroclastics (Toi mine, Japan). If you start seeing quartz, adularia, rhodochrosite in float, you are in the right ground. Typical habit: aggregates, micaceous, spherical. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify truscottite?+
Where is truscottite found?+
What rocks look like truscottite?+
What minerals are found with truscottite?+
What kind of rock does truscottite form in?+
What is truscottite used for?+
Find truscottite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
