How to identify Calcite with Hematite

To correctly identify Calcite with Hematite (Calcite (CaCO3) with Hematite (Fe2O3) inclusions), 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, orange, and reddish-brown to deep red, depending on the concentration and oxidation state of the hematite inclusions. The calcite matrix itself is typically white or colorless.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to sub-vitreous on crystal faces, dull to earthy on massive forms. Hematite inclusions can sometimes impart a sub-metallic sheen if present as larger flakes.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Can be crystalline, massive, granular, or stalactitic. The hematite inclusions may appear as fine dust, specks, or distinct layers within the calcite.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Calcite typically forms rhombohedral, scalenohedral, prismatic, or tabular crystals. Hematite inclusions often follow the growth patterns of the calcite host, sometimes creating phantom crystals or zoned coloration.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect rhombohedral cleavage in three directions, producing characteristic rhomb-shaped fragments. This is a key diagnostic feature of calcite.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, sedimentary carbonate rocks (limestones, dolostones), metamorphic skarns, and cave formations (speleothems). Often found in association with iron ore deposits or areas with significant iron mineralization.

Key Facts

Hardness

3 on the Mohs scale (for calcite), 5-6 (for hematite)

Specific Gravity

2.71 (for pure calcite), 5.26 (for pure hematite); the aggregate will be between these values depending on the proportion of hematite.

Crystal System

Trigonal (for calcite), Trigonal (for hematite)

Color

Red, reddish-brown, pink, orange

Luster

Vitreous to sub-vitreous

Transparency

Transparent to translucent (calcite), opaque (hematite)

Fracture

Conchoidal to uneven (calcite)

Cleavage

Perfect rhombohedral in three directions (calcite)

Composition

Calcium carbonate (CaCO3) with iron oxide (Fe2O3) inclusions

Physical characteristics

• Crystal Habit: Rhombohedral, scalenohedral, prismatic, tabular, massive, granular, stalactitic. Hematite inclusions often highlight growth zones.
• Cleavage Type: Perfect rhombohedral {1011}
• Fracture Type: Conchoidal to uneven
• Tenacity: Brittle
• Luster Type: Vitreous to sub-vitreous

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