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, 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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