Niter, commonly known as saltpeter, typically forms as delicate, hair-like efflorescences or thin crusts in extremely arid environments such as cave walls or dry soil. It is water-soluble and highly hygroscopic, making it difficult to preserve in humid conditions; collectors should store it in sealed containers.
Is this niter?
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 niter with a known reference. Niter sits at Mohs 2, 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: vitreous.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: encrustations, massive.
Often confused with
Niter vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside niter
Minerals reported to co-occur with niter. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KNO₃
- Mohs hardness
- 2
- Density
- 2.109 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Encrustations, massive
- Cleavage
- {011}, nearly perfect; {010}, good; {110}, imperfect
- Rarity
- Uncommon
- Uses
- Collector, Historical manufacture of gunpowder, Fertilizer
- Host rock
- In some caves, typically formed by bacterial action on animal matter, as bat guano, or from vegetable matter, such as humus, exposed to seeping groundwater; an efflorescence on soils or cliff faces in arid regions
Where rockhounds find niter
1 mapped spotsClassic worldwide localities
- Lava tubes 16 km east of Lava Station, Socorro Co., New Mexico, USA
- Usually in minor amounts, but may form substantial masses, into the thousands of tons, especially in some cave deposits
- Typical large-scale occurrences are represented by: Pulo di Molfetta Cave, Apulia, Italy
- Rusensky Lom Cave, Bulgaria
Field-hunting tip
Where it forms: In some caves, typically formed by bacterial action on animal matter, as bat guano, or from vegetable matter, such as humus, exposed to seeping groundwater; an efflorescence on soils or cliff faces in arid regions. If you start seeing nitratine, nitrocalcite, nitromagnesite in float, you are in the right ground. Typical habit: encrustations, massive. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah. Start trip planning there.
Common questions
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Find niter on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
