Kilchoanite is a rare calcium silicate mineral typically found in high-temperature contact metamorphic zones. It usually occurs as fine-grained masses or lamellar intergrowths associated with other skarn minerals like rankinite and larnite. It is primarily a collector's mineral of interest for those specializing in rare silicate species from specific localities like Ardnamurchan.
Is this kilchoanite?
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 kilchoanite with a known reference. Kilchoanite sits at Mohs 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: orthorhombic. Typical habit: lamellar, massive, granular.
Often confused with
Kilchoanite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside kilchoanite
Minerals reported to co-occur with kilchoanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃Si₂O₇
- Mohs hardness
- 5
- Density
- 2.992 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Lamellar, massive, granular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Retrograde replacement of rankinite
Where rockhounds find kilchoanite
Classic worldwide localities
- Kilchoan, Ardnamurchan, Argyllshire, Scotland
- Carlingford, Co. Louth, Ireland
- Golden Gully, Tokatoka district, about 150 km north of Auckland, New Zealand
- Fuka, near Bicchu, Okayama Prefecture, Japan
- Ozerskii massif, near Lake Baikal, eastern Siberia, Russia
Field-hunting tip
Where it forms: Retrograde replacement of rankinite. If you start seeing rankinite, spurrite, tilleyite in float, you are in the right ground. Typical habit: lamellar, massive, granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kilchoanite?+
Where is kilchoanite found?+
What rocks look like kilchoanite?+
What minerals are found with kilchoanite?+
What kind of rock does kilchoanite form in?+
What is kilchoanite used for?+
Find kilchoanite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
