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, 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.
