Jennite is a rare calcium silicate hydrate typically found in metamorphosed limestone deposits. It is best identified by its distinctive pink or white acicular, radiating spray habit and soft, pearly luster.
Is this jennite?
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 jennite with a known reference. Jennite sits at Mohs 3.5, 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.
- 5Look at form & habitCrystal system: triclinic. Typical habit: bladed, platy.
Often confused with
Jennite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside jennite
Minerals reported to co-occur with jennite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₉Si₆O₁₈(OH)₆·8H₂O
- Mohs hardness
- 3.5
- Density
- 2.32-2.33 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Bladed, platy
- Cleavage
- Distinct on {001}
- Fluorescence
- Weak white under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late-stage mineral, partially filling open spaces and in veins in fractured contact metamorphic rocks
Where rockhounds find jennite
Classic worldwide localities
- Crestmore, Riverside Co., California, USA
- Campomorto, Montalto di Castro, Lazio, Italy
- Bellerberg volcano, two km north of Mayen, Eifel district, and Zeilberg, near Maroldsweisach, Bavaria, Germany
- Hatrurim Formation, Israel
- Wessels mine, near Kuruman, Cape Province, South Africa
- Fuka, near Bicchu, Okayama Prefecture, Japan
Field-hunting tip
Where it forms: A late-stage mineral, partially filling open spaces and in veins in fractured contact metamorphic rocks. If you start seeing tobermorite, scawtite, calcite in float, you are in the right ground. Typical habit: bladed, platy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify jennite?+
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What rocks look like jennite?+
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Find jennite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
