How to identify Larimar

To correctly identify Larimar (Pectolite (variety Larimar)), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Ranges from white, light-blue, sky-blue, to greenish-blue, often with white mottling and sometimes reddish-brown inclusions. The most desirable color is a vibrant sky-blue.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Silky to vitreous when polished, dull to sub-vitreous in rough form.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically massive, with a fine-grained, fibrous texture. Can appear mottled or streaky due to variations in color and white pectolite.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Usually massive, compact, or fibrous aggregates. Individual crystals are acicular (needle-like) but rarely visible to the naked eye.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect in two directions at 90 degrees, though rarely observed in massive material.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found exclusively in amygdaloidal cavities and fractures within basaltic volcanic rocks, formed through hydrothermal alteration processes.

Key Facts

Hardness

4.5-5 on the Mohs scale

Specific Gravity

2.74-2.88

Crystal System

Triclinic

Color

Blue, sky-blue, greenish-blue, white, often mottled

Luster

Silky to vitreous

Transparency

Translucent to opaque

Fracture

Uneven to splintery

Cleavage

Perfect in two directions at 90 degrees

Composition

Hydrous sodium calcium silicate

Physical characteristics

• Crystal Habit: Massive, compact, fibrous aggregates; individual crystals are acicular (needle-like) but microscopic.
• Cleavage Type: Perfect on {100} and {001} at 90 degrees.
• Fracture Type: Uneven to splintery.
• Tenacity: Brittle.
• Luster Type: Silky to vitreous on fresh surfaces, dull to sub-vitreous on rough surfaces.

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