Stilbite-Ca is best recognized by its signature sheaf-like or bow-tie crystal clusters that form in vugs within volcanic rock. It is a common zeolite that often appears alongside other minerals like apophyllite and heulandite in basalt cavities, making it a favorite for display specimens.
Is this stilbite-ca?
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 stilbite-ca with a known reference. Stilbite-Ca sits at Mohs 3.5-4, 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, pearly on cleavage.
- 4Match the color rangeCompare against the expected color range: white, red, yellow, brown, cream.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, globular, wheat sheaf.
Often confused with
Stilbite-Ca vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside stilbite-ca
Minerals reported to co-occur with stilbite-ca. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₄(Si₂₇Al₉)O₇₂·28H₂O
- Mohs hardness
- 3.5-4
- Density
- 2.19 g/cm³
- Streak
- White
- Luster
- Vitreous, pearly on cleavage
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, globular, wheat sheaf
- Cleavage
- {010}, perfect
- Rarity
- Common
- Uses
- Collector, Decorative
- Host rock
- A low-temperature hydrothermal mineral, in amygdules and cavities in basalts, andesites, and various metamorphic rocks
Where rockhounds find stilbite-ca
Classic worldwide localities
- Great Notch and Paterson, Passaic Co., New Jersey, USA
- South fork of the Toutle River, Cowlitz Co., and at Skookumchuck Dam, near Bucoda, Thurston Co., Washington, USA
- Goble, Columbia Co., and near Dollar, Lynn Co., Oregon, USA
- Helgustadir mine, Reydarfjord, and the Teigarhorn, Berufjord, Iceland
- Glasgow district, Dumbartonshire, Scotland
- Strzegom (Striegau), Poland
Field-hunting tip
Where it forms: A low-temperature hydrothermal mineral, in amygdules and cavities in basalts, andesites, and various metamorphic rocks. If you start seeing zeolites, prehnite, calcite in float, you are in the right ground. Typical habit: fibrous, globular, wheat sheaf. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify stilbite-ca?+
Where is stilbite-ca found?+
What rocks look like stilbite-ca?+
What minerals are found with stilbite-ca?+
What kind of rock does stilbite-ca form in?+
What is stilbite-ca used for?+
Find stilbite-ca on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
