Calciohilairite is a rare member of the hilairite group characterized by its rhombohedral crystal habit and often translucent to transparent appearance. It is primarily found as a late-stage mineral in alkaline intrusive complexes, most notably at the famous Mont Saint-Hilaire locality where it occurs in cavities.
Is this calciohilairite?
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 calciohilairite with a known reference. Calciohilairite sits at Mohs 4, 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 pearly, dull if altered.
- 4Match the color rangeCompare against the expected color range: blue white, white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: rhombohedral crystals, sometimes rounded or barrel-shaped.
Often confused with
Calciohilairite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Zircon is the harder of the two (Mohs 7.5 vs. 4).
How to tell apart: Catapleiite is the harder of the two (Mohs 5.5-6 vs. 4); luster reads vitreous to pearly, dull if altered on Calciohilairite and weakly vitreous or dull on Catapleiite.
Often found alongside calciohilairite
Minerals reported to co-occur with calciohilairite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaZrSi₃O₉·3H₂O
- Mohs hardness
- 4
- Density
- 2.68 g/cm³
- Colors
- Blue whiteWhite
- Streak
- White
- Luster
- Vitreous to pearly, dull if altered
- Transparency
- Semitransparent
- Crystal system
- Trigonal
- Crystal habit
- Rhombohedral crystals, sometimes rounded or barrel-shaped
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In miarolitic cavities in a peralkalic alaskitic border granite of a batholith (Liberty Bell Mountain, Washington, USA); in miarolitic cavities in a nepheline syenite sill (near Saint-Amable, Canada)
Where rockhounds find calciohilairite
Classic worldwide localities
- Washington Pass, on Liberty Bell Mountain, Okanogan Co., Washington, USA
- Saint-Amable, Quebec, Canada
Field-hunting tip
Where it forms: In miarolitic cavities in a peralkalic alaskitic border granite of a batholith (Liberty Bell Mountain, Washington, USA); in miarolitic cavities in a nepheline syenite sill (near Saint-Amable, Canada). If you start seeing microcline, quartz, albite in float, you are in the right ground. Typical habit: rhombohedral crystals, sometimes rounded or barrel-shaped. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify calciohilairite?+
Where is calciohilairite found?+
What rocks look like calciohilairite?+
What minerals are found with calciohilairite?+
What kind of rock does calciohilairite form in?+
What is calciohilairite used for?+
Find calciohilairite on the map
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