Trimounsite-(Y) is an exceptionally rare yttrium-bearing silicate mineral originally discovered in the Trimouns talc mine of France. It typically occurs as small tabular crystals within dolomitic marble environments associated with hydrothermal activity.
Is this trimounsite-(y)?
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 trimounsite-(y) with a known reference. Trimounsite-(Y) 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: adamantine.
- 4Match the color rangeCompare against the expected color range: light brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic, striated.
Often confused with
Trimounsite-(Y) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Trimounsite-(Y) is noticeably harder (Mohs 7 vs. 5.5-6); streak differs, so Trimounsite-(Y) leaves white, Allanite leaves gray; luster reads adamantine on Trimounsite-(Y) and submetallic on Allanite.
How to tell apart: Trimounsite-(Y) is noticeably harder (Mohs 7 vs. 5-5.5).
Often found alongside trimounsite-(y)
Minerals reported to co-occur with trimounsite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Y₂Ti₂SiO₉
- Mohs hardness
- 7
- Density
- 5.0 g/cm³
- Colors
- Streak
- White
- Luster
- Adamantine
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, striated
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In dolomitic portions of a talc deposit
Where rockhounds find trimounsite-(y)
Classic worldwide localities
- Trimouns talc deposit, 6 km northeast of Luzenac, Ariege, France (type locality)
Field-hunting tip
Where it forms: In dolomitic portions of a talc deposit. If you start seeing allanite, bastnäsite, monazite in float, you are in the right ground. Typical habit: prismatic, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify trimounsite-(y)?+
Where is trimounsite-(y) found?+
What rocks look like trimounsite-(y)?+
What minerals are found with trimounsite-(y)?+
What kind of rock does trimounsite-(y) form in?+
What is trimounsite-(y) used for?+
Find trimounsite-(y) on the map
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