Elpidite is a rare sodium zirconium silicate commonly found as delicate, needle-like prismatic crystals or in fibrous, radiating aggregates. It is most frequently encountered by collectors in high-alkaline environments like Mont Saint-Hilaire or the pegmatites of Greenland. Collectors should look for its distinctive acicular habit often contrasting against dark host minerals.
Is this elpidite?
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 elpidite with a known reference. Elpidite sits at Mohs 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: silky, vitreous to waxy or dull.
- 4Match the color rangeCompare against the expected color range: white, brown, colorless, yellow brown, light red.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous.
Often confused with
Elpidite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads silky, vitreous to waxy or dull on Elpidite and vitreous to pearly on Natrolite.
How to tell apart: Luster reads silky, vitreous to waxy or dull on Elpidite and vitreous to dull on Eudialyte.
Often found alongside elpidite
Minerals reported to co-occur with elpidite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂ZrSi₆O₁₅·3H₂O
- Mohs hardness
- 5
- Density
- 2.52-2.62 g/cm³
- Streak
- White
- Luster
- Silky, vitreous to waxy or dull
- Transparency
- Opaque to translucent and transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous
- Cleavage
- Perfect on {110}
- Fluorescence
- Yellow-green under SW and LW UV
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- In albitized nepheline syenite and associated pegmatites, aegirine-rich granite, and fenites, in a differentiated alkalic massif (Lovozero massif, Russia)
Where rockhounds find elpidite
Classic worldwide localities
- Washington Pass, Okanogan Co., Washington, USA
- Lovozero and Khibiny massifs, Kola Peninsula, Russia
- Ulan-Erge massif, southeastern Tuva, Russia
- Burpala massif, about 120 km north of Lake Baikal, eastern Siberia, Russia
- Tarbagatai, eastern Kazakhstan
- Khan-Bogdinskii granite massif, Gobi, Mongolia
Field-hunting tip
Where it forms: In albitized nepheline syenite and associated pegmatites, aegirine-rich granite, and fenites, in a differentiated alkalic massif (Lovozero massif, Russia). If you start seeing albite, quartz, aegirine in float, you are in the right ground. Typical habit: fibrous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify elpidite?+
Where is elpidite found?+
What rocks look like elpidite?+
What minerals are found with elpidite?+
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What is elpidite used for?+
Find elpidite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
