How to identify Cobaltocalcite

To correctly identify Cobaltocalcite (Cobalt-bearing Calcite (CaCO3)), 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

   Ranges from pale pink to vibrant rose-pink, often with a reddish tint. The intensity of the color is directly related to the concentration of cobalt.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to sub-vitreous, sometimes pearly on cleavage surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Can be massive, granular, botryoidal, mammillary, stalactitic, or in well-formed rhombohedral crystals.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Typically rhombohedral, scalenohedral, prismatic, or tabular. Often found in aggregates or crusts.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect rhombohedral cleavage in three directions, producing characteristic rhomb-shaped fragments.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in the oxidation zones of cobalt-rich hydrothermal ore deposits, often associated with other secondary cobalt minerals (e.g., erythrite), copper minerals, and sometimes nickel minerals. Also occurs in some low-temperature hydrothermal veins.

Key Facts

Hardness

3 on the Mohs scale

Specific Gravity

2.71 g/cm³ (similar to pure calcite, Co substitution has minor effect)

Crystal System

Trigonal

Color

Pink, rose-pink, reddish-pink

Luster

Vitreous to sub-vitreous, sometimes pearly

Transparency

Transparent to translucent

Fracture

Conchoidal to uneven

Cleavage

Perfect rhombohedral in three directions at 74°55'

Composition

Calcium Carbonate (CaCO3) with significant cobalt (Co) substitution for calcium.

Physical characteristics

• Crystal Habit: Rhombohedral, scalenohedral, prismatic, tabular; also massive, granular, botryoidal, mammillary, stalactitic, encrusting.
• Cleavage Type: Perfect rhombohedral {1011}
• Fracture Type: Conchoidal to uneven
• Tenacity: Brittle
• Luster Type: Vitreous to sub-vitreous, pearly on cleavage surfaces

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