Hydroxylellestadite is a complex member of the apatite group that features sulfate and silicate groups in its structure. It typically occurs in contact metamorphic zones, specifically within skarns where it forms through the interaction of limestone with igneous intrusions. Collectors often find it as small prismatic crystals associated with other silicate minerals in skarn assemblages.
Is this hydroxylellestadite?
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 hydroxylellestadite with a known reference. Hydroxylellestadite sits at Mohs 4.5, 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: pale rose, rose-pink, orange.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: prismatic crystals, granular, massive.
Often confused with
Hydroxylellestadite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside hydroxylellestadite
Minerals reported to co-occur with hydroxylellestadite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₁₀(SiO₄)₃(SO₄)₃(OH)₂
- Mohs hardness
- 4.5
- Density
- 3.068 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent to transparent
- Crystal system
- Hexagonal
- Crystal habit
- Prismatic crystals, granular, massive
- Cleavage
- Indistinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In contact metamorphosed limestone (Crestmore)
Where rockhounds find hydroxylellestadite
Classic worldwide localities
- Crestmore, Riverside Co., California, USA
- Cioclovina Cave, SW side of the Şureanu Mountains and in the Oraviţa skarns, about 35 km SSW of Reşita, Romania
- Chichibu mine, Saitama prefecture, Japan
- Combusted spoil heaps at the Kukla mine, Oslavany, and the Ferdinand mine, Zastávka, Rosice-Oslavany coalfield, Czech Republic
Field-hunting tip
Where it forms: In contact metamorphosed limestone (Crestmore). If you start seeing diopside, wollastonite, vesuvianite in float, you are in the right ground. Typical habit: prismatic crystals, granular, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hydroxylellestadite?+
Where is hydroxylellestadite found?+
What rocks look like hydroxylellestadite?+
What minerals are found with hydroxylellestadite?+
What kind of rock does hydroxylellestadite form in?+
What is hydroxylellestadite used for?+
Find hydroxylellestadite on the map
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