How to identify Stilbite

To correctly identify Stilbite (Stilbite-Ca), 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

   White, colorless, pink, salmon, yellow, brown, reddish-brown. Often pale.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to pearly, especially on cleavage surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically forms radiating, sheaf-like, or bow-tie aggregates. Individual crystals are tabular.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Monoclinic, often forming tabular crystals elongated along [100], frequently twinned to produce characteristic sheaf-like or bow-tie aggregates. Also found as divergent, fibrous, or granular masses.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect on {010}, yielding pearly luster on this surface.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Commonly found in amygdaloidal cavities and veins within basaltic and other mafic volcanic rocks. Also occurs in hydrothermal veins, granites, gneisses, and as a diagenetic mineral in some sedimentary rocks.

Key Facts

Hardness

3.5 - 4 on the Mohs scale

Specific Gravity

2.12 - 2.22 g/cm³

Crystal System

Monoclinic

Color

White, colorless, pink, salmon, yellow, brown, reddish-brown

Luster

Vitreous to pearly

Transparency

Transparent to translucent

Fracture

Uneven

Cleavage

Perfect on {010}

Composition

Hydrated calcium sodium aluminum silicate

Physical characteristics

• Crystal Habit: Typically forms tabular crystals, often twinned into characteristic sheaf-like, bow-tie, or fan-shaped aggregates. Also found as divergent, fibrous, or granular masses.
• Cleavage Type: Perfect on {010}
• Fracture Type: Uneven
• Tenacity: Brittle
• Luster Type: Vitreous to pearly

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