Heulandite-Ca is a common member of the zeolite group, best recognized by its characteristic 'coffin-shaped' tabular crystals. It is frequently found in the cavities of basaltic rocks, often occurring in dense, attractive clusters associated with other zeolites and minerals like stilbite or apophyllite.

Hardness

3-3.5

Mohs

Luster

Vitreous to pearly

Streak

White

Transparency

Transparent

mineralcommonHeulandite family

Heulandite-Ca

Hardness: 3-3.5
Luster: Vitreous to pearly
Streak: White
Transparency: Transparent

Is this heulandite-ca?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch heulandite-ca with a known reference. Heulandite-Ca sits at Mohs 3-3.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous to pearly.
4
Match the color range
Compare against the expected color range: white, reddish white, grayish white, brownish white, yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: crystalline, tabular.

Often confused with

Heulandite-Ca vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside heulandite-ca

Minerals reported to co-occur with heulandite-ca. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: (Ca,Na,K)₅(Si₂₇Al₉)O₇₂·26H₂O
Mohs hardness: 3-3.5
Density: 2.2 g/cm³
Colors: White Reddish white Grayish white Brownish white Yellow
Streak: White
Luster: Vitreous to pearly
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Crystalline, tabular
Cleavage: Perfect on {010}
Rarity: Common
Uses: Collector, Specimen
Host rock: Low temperature zeolite found in a wide variety of geologic environments: volcanic rocks, metamorphic rocks, pegmatites, tuffs, and deep-sea sediments

Where rockhounds find heulandite-ca

Classic worldwide localities

Glasgow, Strathclyde (Dumbartonshire), Scotland (type locality)

Field-hunting tip

Where it forms: Low temperature zeolite found in a wide variety of geologic environments: volcanic rocks, metamorphic rocks, pegmatites, tuffs, and deep-sea sediments. If you start seeing stilbite, apophyllite, calcite in float, you are in the right ground. Typical habit: crystalline, tabular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify heulandite-ca?+

Mohs hardness is 3-3.5. Luster: vitreous to pearly. The streak is white. Common colors include white, reddish white, grayish white, brownish white.

Where is heulandite-ca found?+

Notable localities include Glasgow, Strathclyde (Dumbartonshire), Scotland (type locality).

What rocks look like heulandite-ca?+

Heulandite-Ca is most often confused with Stilbite, Chabazite, Laumontite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with heulandite-ca?+

Heulandite-Ca commonly co-occurs with Stilbite, Apophyllite, Calcite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does heulandite-ca form in?+

Where it forms: Low temperature zeolite found in a wide variety of geologic environments: volcanic rocks, metamorphic rocks, pegmatites, tuffs, and deep-sea sediments. Working float back to the host body is the standard way to chase a fresh occurrence.

What is heulandite-ca used for?+

Heulandite-Ca is used in collector, specimen.

Find heulandite-ca on the map

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