Organic (Non-geological)

Horse Chestnut (Buckeye seed)

Aesculus hippocastanum seed

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) →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

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.

Other organic (non-geological) specimens

See all

Firewood (Wood Log)

Lignum (Plant tissue composed of cellulose and lignin)

Organic (Non-geological)

Note: Item is not a geological specimen

Homo sapiens (Dermal Appendage: Pilus)

Organic / Biological

Manganese-coated Sandstone

Clastic sedimentary rock with Manganese Oxide (often Pyrolusite or Psilomelane)

sedimentary

Grass (Organic Matter/Soil)

Poaceae (family of monocotyledonous flowering plants)

Organic Materia (Not a rock or mineral)

Amber

Resinite / Fossilized Tree Resin

mineral

Chert (and/or Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

sedimentary