Tsilaisite is a rare member of the tourmaline group characterized by its significant manganese content, which gives it a distinct yellow or yellow-brown hue. It is typically found as prismatic crystals within lithium-rich pegmatites, often alongside other tourmaline species. Collectors highly prize it due to its scarcity compared to other more common members of the tourmaline group.
Is this tsilaisite?
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 tsilaisite with a known reference. Tsilaisite sits at Mohs ~7, 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: greenish yellow.
- 5Look at form & habitCrystal system: trigonal. Typical habit: prismatic crystals.
Often confused with
Tsilaisite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside tsilaisite
Minerals reported to co-occur with tsilaisite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaMn₃Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH)
- Mohs hardness
- ~7
- Density
- 3.133 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Prismatic crystals
- Cleavage
- Imperfect on {101̄1} and {112̄0}; {0001} parting
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In an aplitic dike in an LCT-type pegmatite
Where rockhounds find tsilaisite
Classic worldwide localities
- Grotta d’Oggi, San Pietro in Campo, Elba, Italy
Field-hunting tip
Where it forms: In an aplitic dike in an LCT-type pegmatite. If you start seeing quartz, k-feldspar, plagioclase in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify tsilaisite?+
Where is tsilaisite found?+
What rocks look like tsilaisite?+
What minerals are found with tsilaisite?+
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Find tsilaisite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
