Andesine is a member of the plagioclase feldspar solid solution series, falling between oligoclase and labradorite in chemical composition. It is commonly found as a rock-forming mineral in intermediate volcanic and plutonic rocks, appearing as white to grey grains in the field.
Is this andesine?
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 andesine with a known reference. Andesine sits at Mohs 6-6.5, 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: subvitreous to pearly.
- 4Match the color rangeCompare against the expected color range: white, gray, greenish, yellowish, reddish, colorless, gray, yellow green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: crystalline, granular.
Often confused with
Andesine vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside andesine
Minerals reported to co-occur with andesine. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na,Ca)(Si,Al)₄O₈
- Mohs hardness
- 6-6.5
- Density
- 2.66-2.68 g/cm³
- Streak
- White
- Luster
- Subvitreous to pearly
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Crystalline, granular
- Cleavage
- Perfect on {001}, less perfect on {010}; {110} also observed
- Rarity
- Common
- Uses
- Collector, Geological study
- Host rock
- Widespread in igneous rocks of intermediate silica content, as syenites and andesites
Where rockhounds find andesine
2 mapped spotsClassic worldwide localities
- Sanford, York Co., Maine, USA
- Andesite lavas of the Andes Mountains, South America, as at Marmato, Columbia
- St. Raphaël, Estérel Mountains, Var, and near Chagey, Haute-Saône, France
- Bodenmais, Bavaria, Germany
- Mt. Arcuentu, Sardinia, Italy
- Vapnefjord, Iceland
Field-hunting tip
Where it forms: Widespread in igneous rocks of intermediate silica content, as syenites and andesites. If you start seeing quartz, potassic feldspar, biotite in float, you are in the right ground. Typical habit: crystalline, granular. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Idaho, Utah. Start trip planning there.
Common questions
How do you identify andesine?+
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Can I find andesine in the United States?+
What rocks look like andesine?+
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Find andesine on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
