Cayalsite-(Y) is a rare calcium yttrium aluminum silicate, typically colorless to faintly pink. It is a late-stage mineral in cavities in yttrian fluorite in granitic NYF-pegmatite. Associated minerals include hematite, vyuntspakhkite-(Y) and hundholmenite-(Y). It was first described from Stetind and Øvre Lapplægeret, Tysfjord, Nordland, Norway.
Is this cayalsite-(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 cayalsite-(y) with a known reference. Cayalsite-(Y) sits at Mohs ~6.5, 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.
- 4Match the color rangeCompare against the expected color range: colorless, faintly pink.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals.
Often confused with
Cayalsite-(Y) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Cayalsite-(Y) leaves white, Gadolinite-(Y) leaves greenish gray.
How to tell apart: Streak differs, so Cayalsite-(Y) leaves white, Allanite leaves gray; luster reads vitreous on Cayalsite-(Y) and submetallic on Allanite.
Often found alongside cayalsite-(y)
Minerals reported to co-occur with cayalsite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaY₆Al₂Si₄O₁₈F₆
- Mohs hardness
- ~6.5
- Density
- 4.81-4.86 g/cm³
- Colors
- ColorlessFaintly pink
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late-stage mineral in cavities in yttrian fluorite in granitic NYF-pegmatite
Where rockhounds find cayalsite-(y)
Classic worldwide localities
- Stetind and Øvre Lapplægeret, Tysfjord, Nordland, Norway
Field-hunting tip
Where it forms: A late-stage mineral in cavities in yttrian fluorite in granitic NYF-pegmatite. If you start seeing bastnäsite-, hematite, vyuntspakhkite- 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 cayalsite-(y)?+
Where is cayalsite-(y) found?+
Is cayalsite-(y) safe to handle?+
What rocks look like cayalsite-(y)?+
What minerals are found with cayalsite-(y)?+
What kind of rock does cayalsite-(y) form in?+
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Find cayalsite-(y) on the map
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