How to identify Ruby in Fuchsite

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

   Distinctive combination of opaque to translucent red (ruby) and vibrant emerald-green (fuchsite).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Ruby is sub-adamantine to vitreous; fuchsite is pearly to vitreous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Granular to schistose, with visible ruby crystals embedded in a micaceous matrix.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Ruby typically forms hexagonal prisms or anhedral grains; fuchsite forms platy, micaceous aggregates.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Ruby has no cleavage (parting may be present); fuchsite exhibits perfect basal cleavage (001).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Metamorphic terrains, particularly those associated with chromium-rich mafic or ultramafic protoliths, often found in greenschist to amphibolite facies metamorphic rocks.

Key Facts

Hardness

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

Specific Gravity

Ruby: 3.95-4.10; Fuchsite: 2.77-2.88

Crystal System

Ruby: Trigonal; Fuchsite: Monoclinic

Color

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

Luster

Ruby: Sub-adamantine to vitreous; Fuchsite: Pearly to vitreous

Transparency

Ruby: Opaque to translucent; Fuchsite: Translucent to opaque

Fracture

Ruby: Conchoidal to uneven; Fuchsite: Uneven

Cleavage

Ruby: None (parting on {0001} and {1011}); Fuchsite: Perfect basal cleavage on {001}

Composition

Ruby: Aluminum oxide (Al2O3) with trace chromium; Fuchsite: Hydrous potassium aluminum silicate with chromium (K(Al,Cr)2(AlSi3O10)(OH)2)

Physical characteristics

• Crystal Habit: Ruby: Hexagonal prisms, tabular, or anhedral grains; Fuchsite: Micaceous, platy, foliated aggregates
• Cleavage Type: Ruby: None (parting); Fuchsite: Perfect basal cleavage
• Fracture Type: Ruby: Conchoidal to uneven; Fuchsite: Uneven
• Tenacity: Ruby: Brittle; Fuchsite: Flexible, elastic
• Luster Type: Ruby: Sub-adamantine to vitreous; Fuchsite: Pearly to vitreous

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