Thomsonite-Sr is a member of the zeolite group most frequently collected for its beautiful radiating, fibrous, and often multi-colored banded patterns in volcanic rock vesicles. It is typically found as radial sprays of needle-like crystals or dense botryoidal masses which polish exceptionally well for lapidary use.
Is this thomsonite-sr?
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 thomsonite-sr with a known reference. Thomsonite-Sr sits at Mohs 5-5.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Thomsonite-Sr leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Thomsonite-Sr typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, yellow, pink, green, brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: radial, fibrous, or acicular aggregates, often forming botryoidal or fan-shaped masses.
Often confused with
Thomsonite-Sr vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside thomsonite-sr
Minerals reported to co-occur with thomsonite-sr. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Sr₂Ca₂(Al₅Si₅O₂₀)·7H₂O
- Mohs hardness
- 5-5.5
- Density
- 2.3-2.4 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Radial, Fibrous, Or Acicular Aggregates, Often Forming Botryoidal or Fan-shaped Masses
- Cleavage
- Perfect in One Direction
- Rarity
- Uncommon
- Uses
- Collector, Lapidary
- Host rock
- Basaltic Volcanic Cavities and Vesicles
- Typical price
- $10-150 depending on specimen size and pattern quality
Where rockhounds find thomsonite-sr
Classic worldwide localities
- Grand Marais, Minnesota, USA
- Khibiny Massif, Russia
- Isle Royale, Michigan, USA
- Bay of Fundy, Nova Scotia, Canada
Field-hunting tip
Look in basaltic volcanic cavities and vesicles country — that is the host setting where thomsonite-sr typically forms. If you start seeing prehnite, analcime, calcite in float, you are in the right ground. Field specimens usually show a radial, fibrous, or acicular aggregates, often forming botryoidal or fan-shaped masses habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify thomsonite-sr?+
Where is thomsonite-sr found?+
How much is thomsonite-sr worth?+
What rocks look like thomsonite-sr?+
What minerals are found with thomsonite-sr?+
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Find thomsonite-sr on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
