Epistolite is a rare mineral found primarily in alkaline igneous rocks like nepheline syenites. It is typically identified by its distinct micaceous or platy appearance, often forming flexible, pearly lamellae that resemble mica but with different chemical properties.
Is this epistolite?
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 epistolite with a known reference. Epistolite sits at Mohs 1.5-3, 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: pearly to silky.
- 4Match the color rangeCompare against the expected color range: white, yellowish white, gray, light brown.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy.
Often confused with
Epistolite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Epistolite leaves white, Lomonosovite leaves light rose-cinnamon; luster reads pearly to silky on Epistolite and vitreous to adamantine on cleavages, greasy on fractures on Lomonosovite.
How to tell apart: Luster reads pearly to silky on Epistolite and vitreous on cleavages, greasy on fractures on Murmanite.
Often found alongside epistolite
Minerals reported to co-occur with epistolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₄TiNb₂(Si₂O₇)₂O₂(OH)₂·4H₂O
- Mohs hardness
- 1.5-3
- Density
- 2.65-2.89 g/cm³
- Streak
- White
- Luster
- Pearly to silky
- Transparency
- Opaque to translucent, transparent in thin sheets
- Crystal system
- Triclinic
- Crystal habit
- Platy
- Cleavage
- Perfect on {001}, distinct on {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A low temperature mineral in alkalic pegmatites, albitites, sodalite xenoliths, and hydrothermal veins
Where rockhounds find epistolite
Classic worldwide localities
- A number of localities in the Ilímaussaq alkaline complex intrusion, southern Greenland
- Lovozero massif, Kola Peninsula, Russia
- Mont Saint-Hilaire and near Saint-Amable, Quebec, Canada
Field-hunting tip
Where it forms: A low temperature mineral in alkalic pegmatites, albitites, sodalite xenoliths, and hydrothermal veins. If you start seeing aegirine, albite, murmanite in float, you are in the right ground. Typical habit: platy. Train your eye for that shape before scanning the outcrop.
Common questions
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Find epistolite on the map
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