Organic (Non-geological)

Horse Chestnut (Buckeye seed)

Aesculus hippocastanum seed

AI-generated identification · may be incorrect

Hardness: Approx 2 (Mohs equivalent, soft organic); Color: Deep mahogany brown with a pale circular scar (hilum); Luster: Glossy/Waxy when fresh; Structure: Ellipsoid organic seed; Specific Gravity: Approx 1.1 (often floats or barely sinks).

Hardness: Approx 2 (Mohs equivalent, soft organic)
Color: Deep mahogany brown with a pale circular scar (hilum)
Luster: Glossy/Waxy when fresh

Identified March 7, 2026More organic (non-geological) →

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Physical properties

Formation & geological history

Produced by deciduous trees of the genus Aesculus; they are contemporary botanical specimens rather than geological formations, though they are often mistaken for polished river stones like Jasper or Chert.

Uses & applications

Historically used for extracting saponins (soap), starch for laundry, or as folk remedies for rheumatism; commonly used in children's games like 'conkers' and as decorative items.

Geological facts

Toxic to humans and most livestock if ingested due to aesculin. In British culture, the game of 'Conkers' involves hitting an opponent's chestnut with one's own until one breaks.

Field identification & locations

Identify by the smooth, leathery nut casing and the prominent light-tan 'eye' or scar; found worldwide in temperate parks and forests. Collectors often dry them, though they eventually shrivel unless lacquered.