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 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Elpidite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Elpidite typically shows a vitreous to pearly luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray, pale yellow, pale pink.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular or prismatic crystals, radiating fibrous masses.
Often confused with
Elpidite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous to pearly on Elpidite and vitreous on Natrolite.
How to tell apart: Luster reads vitreous to pearly on Elpidite and vitreous to silky on Pectolite.
How to tell apart: Luster reads vitreous to pearly on Elpidite and vitreous 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
- 5.5
- Density
- 2.58 g/cm³
- Streak
- White
- Luster
- Vitreous to Pearly
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular or Prismatic Crystals, Radiating Fibrous Masses
- Cleavage
- Perfect On {110}
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Agpaitic Pegmatites and Alkaline Igneous Complexes
- Typical price
- $20-150 thumbnail to cabinet specimen
Where rockhounds find elpidite
Classic worldwide localities
- Narsarsuk, Greenland
- Mont Saint-Hilaire, Quebec, Canada
- Kola Peninsula, Russia
- Lovozero Massif, Russia
Field-hunting tip
Look in agpaitic pegmatites and alkaline igneous complexes country, the host setting where elpidite typically forms. If you start seeing eudialyte, aegirine, microcline in float, you are in the right ground. Field specimens usually show a acicular or prismatic crystals, radiating fibrous masses habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find elpidite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
