Adularia is a low-temperature variety of orthoclase characterized by its distinct pseudo-orthorhombic, diamond-shaped crystal habit. It is famously found in alpine fissure veins where it often appears as glassy, clear to milky crystals associated with chlorite or quartz.
Is this adularia?
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 adularia with a known reference. Adularia sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Adularia leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Adularia typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, pale yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: pseudo-orthorhombic prismatic crystals.
Often confused with
Adularia vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside adularia
Minerals reported to co-occur with adularia. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KAlSi₃O₈
- Mohs hardness
- 6
- Density
- 2.56 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Pseudo-orthorhombic Prismatic Crystals
- Cleavage
- Perfect Basal and Side Pinacoid
- Rarity
- Common
- Uses
- Collector, Gemstone
- Host rock
- Alpine-type Hydrothermal Veins
- Typical price
- $10-100 per specimen
Where rockhounds find adularia
3 mapped spotsClassic worldwide localities
- St. Gotthard Pass, Switzerland
- Adula Mountains, Switzerland
- Pfitsch Valley, Italy
- Norway
- USA
Field-hunting tip
Look in alpine-type hydrothermal veins country — that is the host setting where adularia typically forms. If you start seeing quartz, chlorite, calcite in float, you are in the right ground. Field specimens usually show a pseudo-orthorhombic prismatic crystals habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Michigan — start trip planning there.
Common questions
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Find adularia on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
