Gehlenite is a member of the melilite group that typically forms in contact metamorphosed limestones. Collectors should look for short, prismatic, or tabular tetragonal crystals embedded within skarn mineral assemblages.

Hardness

5-6

Mohs

Luster

Vitreous to resinous

Streak

White to grayish white

Transparency

Transparent to translucent and opaque

mineraluncommonMelilite Group family

Gehlenite

Hardness: 5-6
Luster: Vitreous to resinous
Streak: White to grayish white
Transparency: Transparent to translucent and opaque

Is this gehlenite?

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 gehlenite with a known reference. Gehlenite sits at Mohs 5-6, 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 to grayish white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous to resinous.
4
Match the color range
Compare against the expected color range: gray, brown, colorless, greenish, yellow.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: massive, prismatic, tabular.

Often confused with

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

Often found alongside gehlenite

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

All properties

Chemical formula: Ca₂Al(AlSiO₇)
Mohs hardness: 5-6
Density: 3.038 g/cm³
Colors: Gray Brown Colorless Greenish Yellow
Streak: White to grayish white
Luster: Vitreous to resinous
Transparency: Transparent to translucent and opaque
Crystal system: Tetragonal
Crystal habit: Massive, prismatic, tabular
Cleavage: Distinct on {001}, poor on {110}
Rarity: Uncommon
Uses: Collector, Scientific research
Host rock: In contact metamorphosed impure limestones; in calcium-rich ultramafic volcanic rocks

Where rockhounds find gehlenite

Classic worldwide localities

Crestmore, Riverside Co., California, USA
Tres Hermanas district, Luna Co., New Mexico, USA
Iron Hill, Gunnison Co., Colorado, USA
Scawt Hill, near Larne, and at Carneal, Co. Antrim, Ireland
Bellerberg volcano, two km north of Mayen, Eifel district, Germany
Terneras mine, Velardeña, Durango, Mexico

Field-hunting tip

Where it forms: In contact metamorphosed impure limestones; in calcium-rich ultramafic volcanic rocks. If you start seeing dolomite, calcite, augite in float, you are in the right ground. Typical habit: massive, prismatic, tabular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify gehlenite?+

Mohs hardness is 5-6. Luster: vitreous to resinous. The streak is white to grayish white. Common colors include gray, brown, colorless, greenish.

Where is gehlenite found?+

Notable localities include Crestmore, Riverside Co., California, USA; Tres Hermanas district, Luna Co., New Mexico, USA; Iron Hill, Gunnison Co., Colorado, USA; Scawt Hill, near Larne, and at Carneal, Co. Antrim, Ireland; Bellerberg volcano, two km north of Mayen, Eifel district, Germany.

What rocks look like gehlenite?+

Gehlenite is most often confused with Vesuvianite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with gehlenite?+

Gehlenite commonly co-occurs with Dolomite, Calcite, Augite, Olivine, Nepheline, Leucite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does gehlenite form in?+

Where it forms: In contact metamorphosed impure limestones; in calcium-rich ultramafic volcanic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is gehlenite used for?+

Gehlenite is used in collector, scientific research.

Find gehlenite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.