How to identify Fuchsite with Ruby

To correctly identify Fuchsite with Ruby (Chromian Muscovite with Corundum), 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

   Vibrant green matrix (fuchsite) with distinct red to pinkish-red inclusions (ruby). White or grey minerals (e.g., kyanite, margarite) may also be present.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Fuchsite: Vitreous to pearly, often with a shimmering (aventurescent) quality. Ruby: Adamantine to vitreous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Fuchsite: Foliated, schistose, or massive, often with a flaky or platy appearance. Ruby: Granular to well-formed hexagonal crystals embedded within the fuchsite matrix.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Fuchsite: Micaceous, platy, often in aggregates. Ruby: Hexagonal prisms, barrel-shaped, or anhedral grains.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Fuchsite: Perfect basal cleavage (one direction). Ruby: No cleavage, but parting may be present.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Medium- to high-grade metamorphic terrains, often associated with chromium-rich ultramafic rocks, serpentinites, or metasomatic zones.

Key Facts

Hardness

Fuchsite: 2.5-3 (Mohs); Ruby: 9 (Mohs)

Specific Gravity

Fuchsite: 2.77-2.88; Ruby: 3.97-4.05

Crystal System

Fuchsite: Monoclinic; Ruby: Hexagonal (Trigonal)

Color

Fuchsite: Emerald-green; Ruby: Red to pinkish-red

Luster

Fuchsite: Pearly to vitreous; Ruby: Adamantine to vitreous

Transparency

Fuchsite: Translucent to opaque; Ruby: Transparent to opaque

Fracture

Fuchsite: Uneven; Ruby: Conchoidal to uneven

Cleavage

Fuchsite: Perfect basal (001); Ruby: None, but parting on {0001} and {1011} may be present

Composition

Fuchsite: K(Al,Cr)2(AlSi3O10)(OH)2; Ruby: Al2O3 (with Cr3+ impurity)

Physical characteristics

• Crystal Habit: Fuchsite: Micaceous, platy, foliated; Ruby: Prismatic, tabular, barrel-shaped, granular
• Cleavage Type: Fuchsite: Perfect basal; Ruby: None (parting common)
• Fracture Type: Fuchsite: Uneven; Ruby: Conchoidal to uneven
• Tenacity: Fuchsite: Flexible, elastic; Ruby: Brittle
• Luster Type: Fuchsite: Pearly to vitreous; Ruby: Adamantine to vitreous

Explore Fuchsite with Ruby