How to identify Botryoidal Hematite

To correctly identify Botryoidal Hematite (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

   Typically dark steel-gray to black with a metallic luster, or dull reddish-brown to red in earthy varieties. The botryoidal habit often presents a dark, shiny surface.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Metallic to submetallic in the botryoidal form, sometimes dull or earthy in other habits.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Distinctive rounded, globular, or mammillary (breast-like) surface, resembling a bunch of grapes or kidneys. The individual spheres can range from a few millimeters to several centimeters in diameter.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Botryoidal (mammillary, reniform, globular) is the defining characteristic for this specific variety. Hematite itself crystallizes in the trigonal system, but well-formed individual crystals are rare in botryoidal masses.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None observed in botryoidal masses due to its aggregate nature. Hematite itself has no true cleavage but exhibits parting on {0001} and {1011}.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in low-temperature hydrothermal veins, sedimentary iron formations (e.g., Banded Iron Formations), contact metamorphic deposits, and as a weathering product in soils and laterites. The botryoidal habit is particularly common in cavity fillings and concretions.

Key Facts

Hardness

5.5 - 6.5 on the Mohs scale

Specific Gravity

5.26 (relatively heavy for a non-metallic mineral)

Crystal System

Trigonal (though botryoidal forms are aggregates of microscopic crystals)

Color

Steel-gray, black, reddish-brown, red

Luster

Metallic, submetallic, dull, earthy

Transparency

Opaque

Fracture

Uneven to subconchoidal

Cleavage

None (parting on {0001} and {1011} can be observed in crystalline forms, but not typically in botryoidal aggregates)

Composition

Iron oxide (Fe2O3)

Physical characteristics

• Crystal Habit: Botryoidal, mammillary, reniform, globular, massive, micaceous (specular hematite), oolitic, columnar, stalactitic
• Cleavage Type: None
• Fracture Type: Uneven to subconchoidal
• Tenacity: Brittle
• Luster Type: Metallic to submetallic (botryoidal), dull, earthy

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