Xonotlite is a hydrous calcium silicate typically found as dense, fibrous masses or radiating needle-like clusters. It is highly valued by collectors for its fine, silky texture and often forms in high-temperature contact metamorphic environments.
Is this xonotlite?
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 xonotlite with a known reference. Xonotlite sits at Mohs 6-6.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Xonotlite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Xonotlite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, gray, colorless, pink.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, acicular, radiating sprays, or massive.
Often confused with
Xonotlite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Xonotlite is noticeably harder (Mohs 6-6.5 vs. 4.5-5); luster reads pearly on Xonotlite and vitreous on Wollastonite.
How to tell apart: Xonotlite is noticeably harder (Mohs 6-6.5 vs. 4.5-5); luster reads pearly on Xonotlite and vitreous to silky on Pectolite.
How to tell apart: Luster reads pearly on Xonotlite and vitreous on Tremolite.
Often found alongside xonotlite
Minerals reported to co-occur with xonotlite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₆Si₆O₁₇(OH)₂
- Mohs hardness
- 6-6.5
- Density
- 2.7 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, Acicular, Radiating Sprays, Or Massive
- Cleavage
- Perfect
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Metamorphosed Limestone or Skarn Deposits
- Typical price
- $10-100 per specimen
Where rockhounds find xonotlite
Classic worldwide localities
- Mexico
- Japan
- USA
- Canada
- Italy
Field-hunting tip
Look in metamorphosed limestone or skarn deposits country — that is the host setting where xonotlite typically forms. If you start seeing prehnite, calcite, tobermorite in float, you are in the right ground. Field specimens usually show a fibrous, acicular, radiating sprays, or massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find xonotlite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
