Killalaite is a rare calcium silicate mineral typically found in contact metamorphic limestone deposits. It is most frequently encountered as small, colorless platy crystals associated with calc-silicate skarns, making it a highly sought-after species for mineralogists and advanced collectors.

Hardness

5.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Killalaite

Hardness: 5.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this killalaite?

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 killalaite with a known reference. Killalaite sits at Mohs 5.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Killalaite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Killalaite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: trigonal. Typical habit: platy crystals, granular aggregates.

Often confused with

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

mineral

Calcite

Mohs 3

How to tell apart: Killalaite is noticeably harder (Mohs 5.5 vs. 3).

Often found alongside killalaite

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

All properties

Chemical formula: Ca₆Si₂O₇(OH)₂
Mohs hardness: 5.5
Density: 2.84 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Trigonal
Crystal habit: Platy Crystals, Granular Aggregates
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: Metamorphosed Limestone (skarn Deposits)
Typical price: $50-300 per specimen depending on size and rarity

Where rockhounds find killalaite

Classic worldwide localities

Killala Bay, Ireland
Fuka, Japan
Little Belt Mountains, Montana, USA

Field-hunting tip

Look in metamorphosed limestone (skarn deposits) country — that is the host setting where killalaite typically forms. If you start seeing calcite, cuspidine, wollastonite in float, you are in the right ground. Field specimens usually show a platy crystals, granular aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify killalaite?+

Mohs hardness is 5.5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is killalaite found?+

Notable localities include Killala Bay, Ireland; Fuka, Japan; Little Belt Mountains, Montana, USA.

How much is killalaite worth?+

Typical asking prices fall in the range of $50-300 per specimen depending on size and rarity. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like killalaite?+

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

What minerals are found with killalaite?+

Killalaite commonly co-occurs with Calcite, Cuspidine, Wollastonite, Afwillite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does killalaite form in?+

Killalaite typically forms in metamorphosed limestone (skarn deposits). Working float back to the host body is the standard way to chase a fresh occurrence.

What is killalaite used for?+

Killalaite is used in collector.

Find killalaite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.