Martinandresite is an extremely rare calcium-yttrium silicate mineral found almost exclusively in the alkaline rocks of Mont Saint-Hilaire. It typically occurs as delicate, acicular, or fibrous aggregates often associated with other rare silicate minerals in vugs and cavities.
Is this martinandresite?
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 martinandresite with a known reference. Martinandresite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Martinandresite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Martinandresite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular crystals, radial aggregates.
Often confused with
Martinandresite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside martinandresite
Minerals reported to co-occur with martinandresite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₄Y₂Si₄O₁₃(OH)₂·2H₂O
- Mohs hardness
- 3-4
- Density
- 3.36 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular Crystals, Radial Aggregates
- Cleavage
- Distinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Intrusions
- Typical price
- $50-300+ per specimen
Where rockhounds find martinandresite
Classic worldwide localities
- Mont Saint-Hilaire, Quebec, Canada
Field-hunting tip
Look in alkaline igneous intrusions country, the host setting where martinandresite typically forms. If you start seeing analcime, sodalite, microcline in float, you are in the right ground. Field specimens usually show a acicular crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find martinandresite on the map
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