Rock Identifier
Clay Brick (Ceramic structural unit (Al2O3·2SiO2·2H2O as precursor)) — metamorphic (man-made/anthropogenic)
metamorphic (man-made/anthropogenic)

Clay Brick

Ceramic structural unit (Al2O3·2SiO2·2H2O as precursor)

Hardness: 5-6 (Mohs); Color: Red/terracotta due to iron oxide; Luster: Dull/earthy; Structure: Microcrystalline/vitrified; Cleavage: None

Hardness
5-6 (Mohs)
Color
Red/terracotta due to iron oxide
Luster
Dull/earthy

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Physical properties

Hardness: 5-6 (Mohs); Color: Red/terracotta due to iron oxide; Luster: Dull/earthy; Structure: Microcrystalline/vitrified; Cleavage: None

Formation & geological history

Formed through the high-temperature firing (kilning) of alluvial clays and shales. While the raw materials are millions of years old, the 'rock' is created in 24-48 hours via heat-induced vitrification.

Uses & applications

Primary load-bearing and decorative material in construction, architecture, and civil engineering.

Geological facts

Bricks are one of the oldest known building materials, dating back to 7000 BC. The red color is caused by the oxidation of iron minerals during the firing process, similar to the formation of metamorphic rocks.

Field identification & locations

Identified by uniform rectangular shapes, mortar joints, and a porous, gritty texture. Common in urban environments. Collectors rarely value modern bricks, though 'historic' or 'branded' antique bricks (brickbats) are a niche hobby.