How to identify Rhodochrosite with Pyrite

To correctly identify Rhodochrosite with Pyrite (Rhodochrosite (MnCO3) with Pyrite (FeS2)), 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

   Rhodochrosite typically exhibits shades of pink to red, often with white banding. Pyrite is brassy yellow to golden, sometimes with a slight greenish or brownish tint, and can tarnish to a duller brassy color.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Rhodochrosite has a vitreous to pearly luster. Pyrite has a distinct metallic luster.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Rhodochrosite can be massive, botryoidal, stalactitic, or form rhombohedral crystals. Pyrite commonly forms euhedral cubes, octahedra, or pyritohedra, and can also be massive or granular. The texture of the association will depend on the habits of both minerals.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Rhodochrosite: Rhombohedral crystals, often with curved faces; also massive, botryoidal, stalactitic. Pyrite: Cubic, octahedral, pyritohedral crystals; also massive, granular, reniform, or radiating.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Rhodochrosite: Perfect rhombohedral cleavage in three directions, forming angles of 73° and 107°. Pyrite: Indistinct cleavage, typically conchoidal to uneven fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, particularly those associated with manganese and base metal deposits. Also found in some sedimentary and metamorphic environments where both manganese and iron-sulfur rich fluids or conditions were present.

Key Facts

Hardness

Rhodochrosite: 3.5-4 on the Mohs scale. Pyrite: 6-6.5 on the Mohs scale.

Specific Gravity

Rhodochrosite: 3.45-3.70. Pyrite: 4.95-5.10.

Crystal System

Rhodochrosite: Trigonal. Pyrite: Isometric.

Color

Rhodochrosite: Pink, rose-red, reddish-brown. Pyrite: Brassy yellow, golden.

Luster

Rhodochrosite: Vitreous to pearly. Pyrite: Metallic.

Transparency

Rhodochrosite: Transparent to translucent. Pyrite: Opaque.

Fracture

Rhodochrosite: Uneven to conchoidal. Pyrite: Conchoidal to uneven.

Cleavage

Rhodochrosite: Perfect rhombohedral {1011}. Pyrite: Indistinct {001} or {110}.

Composition

Rhodochrosite: Manganese carbonate (MnCO3). Pyrite: Iron disulfide (FeS2).

Physical characteristics

• Crystal Habit: Rhodochrosite: Rhombohedral, botryoidal, stalactitic, massive. Pyrite: Cubic, octahedral, pyritohedral, massive, granular.
• Cleavage Type: Rhodochrosite: Perfect rhombohedral. Pyrite: Indistinct.
• Fracture Type: Rhodochrosite: Uneven to conchoidal. Pyrite: Conchoidal to uneven.
• Tenacity: Rhodochrosite: Brittle. Pyrite: Brittle.
• Luster Type: Rhodochrosite: Vitreous to pearly. Pyrite: Metallic.

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