How to identify Laterite

To correctly identify Laterite (Laterite), 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 reddish-brown to dark red, often mottled with yellow, brown, or black. The color is due to the presence of iron oxides (hematite, goethite).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Dull to earthy, sometimes sub-vitreous in more indurated varieties.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Highly variable, ranging from earthy, porous, and friable to hard, dense, and indurated. Often exhibits pisolitic (pea-sized concretions) or oolitic (egg-shaped concretions) structures. Can also be massive or vesicular.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Amorphous to cryptocrystalline aggregates of various iron and aluminum oxyhydroxides. Individual crystals are rarely macroscopic.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None, as it is a rock composed of fine-grained or amorphous minerals.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Forms in tropical and subtropical regions with high rainfall, high temperatures, and distinct wet and dry seasons. Requires well-drained upland surfaces or gently sloping terrains where chemical weathering is intense and prolonged, leading to the leaching of soluble components from parent rocks (igneous, metamorphic, or sedimentary).

Key Facts

Hardness

Variable, from 1 (earthy) to 7 (indurated, due to quartz or highly cemented iron oxides) on the Mohs scale.

Specific Gravity

2.5 to 3.5, depending on porosity and mineralogical composition.

Crystal System

Amorphous to cryptocrystalline aggregates; individual mineral components (e.g., goethite, hematite, gibbsite) have their own crystal systems (e.g., orthorhombic for goethite, trigonal for hematite, monoclinic for gibbsite).

Color

Reddish-brown, dark red, yellow, brown, black, often mottled.

Luster

Dull, earthy, sometimes sub-vitreous.

Transparency

Opaque.

Fracture

Earthy, conchoidal (in indurated varieties), irregular.

Cleavage

None.

Composition

Primarily hydrated oxides of iron (goethite, hematite, ferrihydrite) and aluminum (gibbsite, boehmite, diaspore), with minor amounts of kaolinite, quartz, and residual primary minerals.

Physical characteristics

• Crystal Habit: Massive, earthy, pisolitic, oolitic, vesicular, concretionary.
• Cleavage Type: Not applicable (no cleavage).
• Fracture Type: Earthy, irregular, sub-conchoidal.
• Tenacity: Friable to brittle, depending on induration.
• Luster Type: Dull to earthy.

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