How to identify Hematite (botryoidal)

To correctly identify Hematite (botryoidal) (Hematite (botryoidal habit)), 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

   Steel-gray to black, reddish-brown, or silver-gray. Botryoidal forms are typically dark gray to black on the surface.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Metallic to submetallic, sometimes dull or earthy. Botryoidal forms often have a submetallic to dull luster.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth, rounded, mammillary, or grape-like masses. The surface can feel slightly rough or granular in some specimens.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Botryoidal (grape-like aggregates), mammillary, reniform (kidney-shaped), massive, micaceous (specular hematite), tabular, or rhombohedral crystals.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None. Hematite exhibits no true cleavage, but may show parting on {0001} and {1011}.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, sedimentary iron formations (BIFs), contact metamorphic deposits, and as an alteration product in igneous and metamorphic rocks. Botryoidal forms are common in low-temperature hydrothermal deposits and as concretions in sedimentary rocks.

Key Facts

Hardness

5.5-6.5 on the Mohs scale

Specific Gravity

5.26 (pure)

Crystal System

Trigonal

Color

Steel-gray, black, reddish-brown, silver-gray

Luster

Metallic, submetallic, dull, earthy

Transparency

Opaque

Fracture

Uneven to subconchoidal

Cleavage

None (parting on {0001} and {1011})

Composition

Iron oxide (Fe2O3)

Physical characteristics

• Crystal Habit: Botryoidal, mammillary, reniform, massive, micaceous, tabular, rhombohedral
• Cleavage Type: None, but parting on {0001} and {1011} is common
• Fracture Type: Uneven to subconchoidal
• Tenacity: Brittle
• Luster Type: Metallic to submetallic, dull, earthy

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