sedimentary

Limestone (specifically a Crushed Aggregate fragment)

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale); Color: White to light grey; Luster: Dull/Earthy; Crystal Structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific Gravity: 2.7.

Hardness: 3 (Mohs scale)
Color: White to light grey
Luster: Dull/Earthy

Identified April 25, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: White to light grey; Luster: Dull/Earthy; Crystal Structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific Gravity: 2.7.

Formation & geological history

Formed through the accumulation of shell, coral, algal, and fecal debris in marine environments. This specific specimen appears to be a fragment of mechanically crushed quarry stone used in construction.

Uses & applications

Primary source of lime for cement, used as a soil conditioner in agriculture, road base aggregate, and white pigment or filler in toothpaste and plastics.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary building block of the Great Pyramids of Giza.

Field identification & locations

Identify in the field by its softness (can be scratched by a copper coin) and its effervescence (bubbles) when a drop of weak acid such as vinegar is applied. Very common in regions with ancient seabed history.