How to identify Tremolite

To correctly identify Tremolite (Ca2Mg5Si8O22(OH)2), 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

   Typically white, gray, light green, or colorless. Can be dark green if iron is present (transitioning towards actinolite).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to silky, especially in fibrous varieties.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Can be prismatic, columnar, fibrous, or granular. Fibrous varieties are often soft and flexible.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Monoclinic system, typically forming long, slender, prismatic crystals with a diamond-shaped cross-section (due to amphibole cleavage angles of approximately 56 and 124). Also occurs as radiating aggregates or massive forms.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect cleavage in two directions intersecting at approximately 56 and 124, characteristic of amphiboles.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Metamorphosed dolomitic limestones, marbles, talc schists, and ultramafic rocks. Often associated with minerals like calcite, dolomite, talc, diopside, and serpentine.

Key Facts

Hardness

5-6 on the Mohs scale

Specific Gravity

2.9-3.2 g/cm

Crystal System

Monoclinic

Color

White, gray, light green, colorless

Luster

Vitreous to silky

Transparency

Transparent to translucent to opaque

Fracture

Uneven to subconchoidal

Cleavage

Perfect in two directions at approximately 56 and 124

Composition

Calcium magnesium silicate hydroxide (Ca2Mg5Si8O22(OH)2)

Physical characteristics

• Crystal Habit: Prismatic, columnar, fibrous, radiating, massive, granular
• Cleavage Type: Perfect on {110} (two directions at ~56 and 124)
• Fracture Type: Uneven to subconchoidal
• Tenacity: Brittle (non-fibrous); flexible (fibrous)
• Luster Type: Vitreous to silky

Explore Tremolite