Microsommite is a rare tectosilicate mineral primarily known from the ejecta blocks of Mount Vesuvius and Monte Somma. It typically appears as small, colorless to yellowish hexagonal prisms associated with other alkaline volcanic minerals.
Is this microsommite?
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 microsommite with a known reference. Microsommite sits at Mohs 6, 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: silky to brilliant on {1010}, otherwise vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: crystalline, prismatic, striated.
Often confused with
Microsommite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads silky to brilliant on {1010}, otherwise vitreous on Microsommite and vitreous, pearly, or greasy on Cancrinite.
How to tell apart: Luster reads silky to brilliant on {1010}, otherwise vitreous on Microsommite and vitreous to greasy on Nepheline.
Often found alongside microsommite
Minerals reported to co-occur with microsommite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- [(Na,K)₆(SO₄)][Ca₂Cl₂][(Si₆Al₆O₂₄)]
- Mohs hardness
- 6
- Density
- 2.42-2.53 g/cm³
- Streak
- White
- Luster
- Silky to brilliant on {1010}, otherwise vitreous
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Crystalline, prismatic, striated
- Cleavage
- {1010}, perfect; {0001}, less distinct
- Fluorescence
- Bright yellow under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In ejected volcanic masses and in leucitites
Where rockhounds find microsommite
Classic worldwide localities
- Monte Somma, Campania, and at Pitigliano, near Grosseto, Tuscany, Italy
Field-hunting tip
Where it forms: In ejected volcanic masses and in leucitites. If you start seeing nepheline in float, you are in the right ground. Typical habit: crystalline, prismatic, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify microsommite?+
Where is microsommite found?+
What rocks look like microsommite?+
What minerals are found with microsommite?+
What kind of rock does microsommite form in?+
What is microsommite used for?+
Find microsommite on the map
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