Fantappièite is an exceptionally rare member of the cancrinite group found in volcanic ejected blocks. It typically forms as small, colorless to white prismatic crystals and is primarily known from the unique mineralogical site of Pitigliano in Italy.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareCancrinite Group family

Fantappièite

Hardness: 6
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this fantappièite?

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 fantappièite with a known reference. Fantappièite sits at Mohs 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.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: trigonal. Typical habit: prismatic crystals.

Often confused with

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

Often found alongside fantappièite

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

All properties

Chemical formula: [Na₈₂.₅Ca₃₃K₁₆.₅]Σ=132(Si₉₉Al₉₉O₃₉₆)(SO₄)₃₃·6H₂O
Mohs hardness: 6
Density: 2.471 g/cm³
Colors: Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Trigonal
Crystal habit: Prismatic crystals
Cleavage: Poor on {001}
Rarity: Rare
Uses: Collector
Host rock: In miarolitic cavities within volcanic ejecta

Where rockhounds find fantappièite

Classic worldwide localities

Torre Stracciacappe, Trevignano community, Rome, Latium, Italy

Field-hunting tip

Where it forms: In miarolitic cavities within volcanic ejecta. If you start seeing sanidine, plagioclase, biotite in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify fantappièite?+

Mohs hardness is 6. Luster: vitreous. The streak is white. Common colors include colorless.

Where is fantappièite found?+

Notable localities include Torre Stracciacappe, Trevignano community, Rome, Latium, Italy.

What rocks look like fantappièite?+

Fantappièite is most often confused with Cancrinite, Vishnevite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with fantappièite?+

Fantappièite commonly co-occurs with Sanidine, Plagioclase, Biotite, Augitic clinopyroxene, Andradite, Iron oxides. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does fantappièite form in?+

Where it forms: In miarolitic cavities within volcanic ejecta. Working float back to the host body is the standard way to chase a fresh occurrence.

What is fantappièite used for?+

Fantappièite is used in collector.

Find fantappièite on the map

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