sedimentary

Limestone with Iron Inclusions

Calcium Carbonate (CaCO3) with Hematite/Limonite

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale); Color: White to light grey with rusty brown/red staining; Luster: Dull or earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None/Fragmental; Specific Gravity: 2.3-2.7

Hardness: 3 (Mohs scale)
Color: White to light grey with rusty brown/red staining
Luster: Dull or earthy

Identified June 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily from the accumulation of shell, coral, algal, and fecal debris in clear, warm, shallow marine waters. The brown iron inclusions are likely due to secondary oxidation or groundwater mineral precipitation.

Uses & applications

Limestone is used as a construction material, an aggregate for the base of roads, in cement manufacture, and as an industrial source of calcium.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary building block of most karst landscapes and cave systems.

Field identification & locations

Identify in the field by its softness (can be scratched by a copper coin) and its effervescence (bubbling) when a drop of weak acid such as vinegar is applied. The rusty spots help locate mineral-rich water paths.