Törnebohmite-(La) is a rare silicate mineral belonging to the törnebohmite group, typically found in rare-earth element deposits. It is most frequently encountered as olive-green granular masses associated with other rare-earth minerals like bastnäsite and cerite in skarn environments.
Is this törnebohmite-(la)?
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 törnebohmite-(la) with a known reference. Törnebohmite-(La) 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 to greasy.
- 4Match the color rangeCompare against the expected color range: green, bright olive green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: granular, massive, or small tabular crystals.
Often confused with
Törnebohmite-(La) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Törnebohmite-(La) leaves white, Allanite leaves gray; luster reads vitreous to greasy on Törnebohmite-(La) and submetallic on Allanite.
How to tell apart: Epidote is the harder of the two (Mohs 6-7 vs. 5); streak differs, so Törnebohmite-(La) leaves white, Epidote leaves grayish white.
How to tell apart: Luster reads vitreous to greasy on Törnebohmite-(La) and resinous on Monazite.
Often found alongside törnebohmite-(la)
Minerals reported to co-occur with törnebohmite-(la). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- La₂Al(SiO₄)₂(OH)
- Mohs hardness
- 5
- Density
- 4.805 g/cm³
- Colors
- GreenBright olive green
- Streak
- White
- Luster
- Vitreous to greasy
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Granular, massive, or small tabular crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Replaces cerite, in turn replacing bastnäsite, in granite pegmatite in the fenitization zone of a nepheline syenite massif
Where rockhounds find törnebohmite-(la)
Classic worldwide localities
- Mochalin Log, Kyshtym district, Southern Ural Mountains, Russia
Field-hunting tip
Where it forms: Replaces cerite, in turn replacing bastnäsite, in granite pegmatite in the fenitization zone of a nepheline syenite massif. If you start seeing cerite, bastnäsite, allanite in float, you are in the right ground. Typical habit: granular, massive, or small tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify törnebohmite-(la)?+
Where is törnebohmite-(la) found?+
What rocks look like törnebohmite-(la)?+
What minerals are found with törnebohmite-(la)?+
What kind of rock does törnebohmite-(la) form in?+
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Find törnebohmite-(la) on the map
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