Harmotome is a barium-rich zeolite typically recognized by its distinctive, cross-shaped (cruciform) penetration twins. It is most often found as secondary mineral deposits lining cavities in basaltic rocks or within low-temperature hydrothermal veins.
Is this harmotome?
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 harmotome with a known reference. Harmotome sits at Mohs 4.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Harmotome leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Harmotome typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, gray, yellowish, pink, brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: cruciform penetration twins, prismatic crystals.
Often confused with
Harmotome vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside harmotome
Minerals reported to co-occur with harmotome. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ba,Ca,K,Na)₂₅(Si,Al)₁₀₀O₂₀₀·60H₂O
- Mohs hardness
- 4.5
- Density
- 2.4-2.5 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Cruciform Penetration Twins, Prismatic Crystals
- Cleavage
- Good On {010}
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Volcanic Rocks, Hydrothermal Veins
- Typical price
- $10-100 per specimen
Where rockhounds find harmotome
Classic worldwide localities
- Andreasberg, Germany
- Strontian, Scotland
- Morven, Scotland
- Kongsberg, Norway
- Bay of Fundy, Canada
Field-hunting tip
Look in volcanic rocks, hydrothermal veins country — that is the host setting where harmotome typically forms. If you start seeing calcite, quartz, barite in float, you are in the right ground. Field specimens usually show a cruciform penetration twins, prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify harmotome?+
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Find harmotome on the map
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