Cancrisilite is a rare member of the cancrinite group, often found within alkaline intrusive complexes. It is chemically distinguished by its carbonate-rich composition and is typically identified by its hexagonal habit and association with other feldspathoid minerals.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent to translucent

mineralrareCancrinite Group family

Cancrisilite

Hardness: 5
Luster: Vitreous
Streak: White
Transparency: Transparent to translucent

Is this cancrisilite?

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 cancrisilite with a known reference. Cancrisilite sits at Mohs 5, 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: lilac, colorless, gray, light violet, pink.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: prismatic crystals.

Often confused with

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

Often found alongside cancrisilite

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

All properties

Chemical formula: Na₇(Si₇Al₅)O₂₄(CO₃)·3H₂O
Mohs hardness: 5
Density: 2.40 g/cm³
Colors: LilacColorless Gray Light violet Pink
Streak: White
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Hexagonal
Crystal habit: Prismatic crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In ultra-agpaitic pegmatites in a differentiated alkalic massif

Where rockhounds find cancrisilite

Classic worldwide localities

Mts. Alluaiv and Karnasurt, and in the Chinglusuai River valley, Lovozero massif, Kola Peninsula, Russia

Field-hunting tip

Where it forms: In ultra-agpaitic pegmatites in a differentiated alkalic massif. If you start seeing potassic feldspar, nepheline, sodalite 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 cancrisilite?+

Mohs hardness is 5. Luster: vitreous. The streak is white. Common colors include lilac, colorless, gray, light violet.

Where is cancrisilite found?+

Notable localities include Mts. Alluaiv and Karnasurt, and in the Chinglusuai River valley, Lovozero massif, Kola Peninsula, Russia.

What rocks look like cancrisilite?+

Cancrisilite 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 cancrisilite?+

Cancrisilite commonly co-occurs with Potassic feldspar, Nepheline, Sodalite, Arfvedsonite, Aegirine, Manaksite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does cancrisilite form in?+

Where it forms: In ultra-agpaitic pegmatites in a differentiated alkalic massif. Working float back to the host body is the standard way to chase a fresh occurrence.

What is cancrisilite used for?+

Cancrisilite is used in collector.

Find cancrisilite on the map

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