Silvialite is a rare sulfate-rich member of the scapolite group, typically found in high-grade metamorphic rocks. It is visually indistinguishable from other scapolites without chemical analysis, though its specific sulfate content is its defining characteristic. Collectors typically find it in small, prismatic crystals within calc-silicate assemblages.
Is this silvialite?
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 silvialite with a known reference. Silvialite sits at Mohs ~5.5, 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: subvitreous.
- 4Match the color rangeCompare against the expected color range: slightly yellowish white, colorless.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: granular, subhedral crystals.
Often confused with
Silvialite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside silvialite
Minerals reported to co-occur with silvialite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₄Al₆Si₆O₂₄(SO₄)
- Mohs hardness
- ~5.5
- Density
- 2.75 g/cm³
- Colors
- Slightly yellowish whiteColorless
- Streak
- White
- Luster
- Subvitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Granular, subhedral crystals
- Cleavage
- Good on {100}
- Fluorescence
- Orange under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In granulite facies metamorphic rocks, in mafic and ultramafic xenoliths from the lower crust or upper mantle, and in anorthosites in a meteorite-impact structure
Where rockhounds find silvialite
Classic worldwide localities
- McBride Province, North Queensland, Australia (type locality)
Field-hunting tip
Where it forms: In granulite facies metamorphic rocks, in mafic and ultramafic xenoliths from the lower crust or upper mantle, and in anorthosites in a meteorite-impact structure. If you start seeing plagioclase, calcic amphibole, clinopyroxene in float, you are in the right ground. Typical habit: granular, subhedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify silvialite?+
Where is silvialite found?+
What rocks look like silvialite?+
What minerals are found with silvialite?+
What kind of rock does silvialite form in?+
What is silvialite used for?+
Find silvialite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
