Marinellite is a rare silicate mineral belonging to the cancrinite group, typically found in volcanic rocks in the Alban Hills region of Italy. It usually occurs as small, colorless or white prismatic crystals embedded in volcanic matrices. Collectors prize it primarily as a rare locality-specific species from the Italian alkaline volcanic provinces.
Is this marinellite?
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 marinellite with a known reference. Marinellite sits at Mohs 5.5, 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: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: trigonal. Typical habit: anhedral grains.
Often confused with
Marinellite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside marinellite
Minerals reported to co-occur with marinellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₄₂Ca₆Al₃₆Si₃₆O₁₄₄(SO₄)₈Cl₂(H₂O)₆
- Mohs hardness
- 5.5
- Density
- 2.405 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Anhedral grains
- Cleavage
- Poor on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a highly-reacted xenolith of evaporitic rock as volcanic ejecta
Where rockhounds find marinellite
Classic worldwide localities
- Sacrofano volcano, Biacchella Valley, Latium, Italy
Field-hunting tip
Where it forms: In a highly-reacted xenolith of evaporitic rock as volcanic ejecta. If you start seeing giuseppettite, sanidine, nepheline in float, you are in the right ground. Typical habit: anhedral grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify marinellite?+
Where is marinellite found?+
What rocks look like marinellite?+
What minerals are found with marinellite?+
What kind of rock does marinellite form in?+
What is marinellite used for?+
Find marinellite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
