How to identify Calcite with Hematite

To correctly identify Calcite with Hematite (Calcite (CaCO3) with Hematite (Fe2O3)), 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, salmon, orange, red, to reddish-brown, depending on the hematite content and distribution. Pure calcite is typically white or colorless.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to sub-vitreous for calcite; hematite can impart a duller, earthy, or sub-metallic sheen if abundant on surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically crystalline, often with well-formed calcite crystals. Hematite may appear as fine dust, coatings, or small inclusions.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Calcite commonly forms rhombohedra, scalenohedra, prismatic, or tabular crystals. Hematite can be massive, botryoidal, reniform, or micaceous (specular hematite) within or on the calcite.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect rhombohedral cleavage in three directions, characteristic of calcite (1011).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, sedimentary carbonate rocks, metamorphic rocks, and sometimes in oxidized zones of ore deposits.

Key Facts

Hardness

Calcite: 3 (Mohs); Hematite: 5-6.5 (Mohs). The overall hardness will be dominated by calcite if hematite is an inclusion or coating.

Specific Gravity

Calcite: 2.71 g/cm³; Hematite: 5.26 g/cm³. The specific gravity of the association will be intermediate, depending on the proportion of hematite.

Crystal System

Calcite: Trigonal; Hematite: Trigonal

Color

Pink, red, orange, reddish-brown (due to hematite); otherwise white or colorless (pure calcite).

Luster

Vitreous to sub-vitreous (calcite); earthy, dull, or sub-metallic (hematite).

Transparency

Transparent to translucent (calcite); opaque (hematite). The association can be translucent to opaque.

Fracture

Conchoidal to uneven (calcite); uneven to sub-conchoidal (hematite).

Cleavage

Perfect rhombohedral in three directions (calcite); none (hematite).

Composition

Calcium Carbonate (CaCO3) with Iron Oxide (Fe2O3)

Physical characteristics

• Crystal Habit: Calcite: Rhombohedral, scalenohedral, prismatic, tabular, massive, granular. Hematite: Massive, botryoidal, reniform, micaceous, platy, granular, oolitic.
• Cleavage Type: Calcite: Perfect rhombohedral (1011). Hematite: None.
• Fracture Type: Calcite: Conchoidal to uneven. Hematite: Uneven to sub-conchoidal.
• Tenacity: Calcite: Brittle. Hematite: Brittle.
• Luster Type: Calcite: Vitreous to sub-vitreous. Hematite: Metallic, sub-metallic, dull, earthy.

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