How to identify Larimar

To correctly identify Larimar (Pectolite), 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 light blue to sky blue, greenish-blue, and deep blue, often with white, gray, or reddish-brown streaks and patterns. The blue color is typically unevenly distributed.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

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

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically massive, fibrous, or radiating aggregates. When polished, it feels smooth.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Usually found as 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 on {100} and {001}, often difficult to observe in massive forms.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Occurs exclusively in vugs and fractures within highly altered basaltic and andesitic volcanic rocks, particularly within pillow lavas, where it forms through hydrothermal activity.

Key Facts

Hardness

4.5 - 5 on the Mohs scale

Specific Gravity

2.74 - 2.90

Crystal System

Triclinic

Color

Blue, sky blue, greenish-blue, often with white, gray, or reddish-brown patterns.

Luster

Vitreous to silky (when polished), dull to sub-vitreous (rough).

Transparency

Translucent to opaque.

Fracture

Uneven to splintery.

Cleavage

Perfect on {100} and {001}.

Composition

Hydrous sodium calcium silicate (NaCa2Si3O8(OH)) with trace copper.

Physical characteristics

• Crystal Habit: Typically massive, compact, or fibrous aggregates; individual crystals are acicular (needle-like) but microscopic.
• Cleavage Type: Perfect in two directions ({100} and {001}), forming angles of approximately 90 degrees.
• Fracture Type: Uneven to splintery, due to its fibrous nature.
• Tenacity: Brittle.
• Luster Type: Vitreous to silky, especially on polished surfaces; dull to sub-vitreous on rough surfaces.

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