Sacrofanite is a rare member of the cancrinite group, occurring primarily in volcanic ejecta found within the Roman volcanic province. It typically forms small, prismatic crystals with a vitreous luster, often found associated with minerals like calcite and sanidine in cavity linings. Because it is highly specific to a single geologic province, specimens are highly sought after by systematic mineral collectors.
Is this sacrofanite?
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 sacrofanite with a known reference. Sacrofanite sits at Mohs 5.5-6, 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: pearly.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: hexagonal, prismatic.
Often confused with
Sacrofanite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside sacrofanite
Minerals reported to co-occur with sacrofanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na₆₁K₁₉Ca₃₂)(Si₈₄Al₈₄O₃₃₆)(SO₄)₂₆Cl₂F₆·2H₂O
- Mohs hardness
- 5.5-6
- Density
- 2.423 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Hexagonal, prismatic
- Cleavage
- Perfect on {0001}, {0110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As crystals lining a cavity in an ejected block of volcanic rock
Where rockhounds find sacrofanite
Classic worldwide localities
- Valle Biachella, 3.2 km north-northwest of Sacrofano, in the Sacrofano caldera, Lazio, Italy
Field-hunting tip
Where it forms: As crystals lining a cavity in an ejected block of volcanic rock. If you start seeing sanidine, andradite, fassaite in float, you are in the right ground. Typical habit: hexagonal, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify sacrofanite?+
Where is sacrofanite found?+
What rocks look like sacrofanite?+
What minerals are found with sacrofanite?+
What kind of rock does sacrofanite form in?+
What is sacrofanite used for?+
Find sacrofanite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
