Man-made material (Anthropogenic 'mineraloid')

Sea Glass (Frosted Glass)

Amorphous Silica (SiO2) with various additives

Hardness: 5.5–7 (Mohs scale); Color: Translucent white/clear (frosted); Luster: Vitreous to waxy/frosted; Crystal Structure: Amorphous (none); Cleavage: Conchoidal fracture; Specific Gravity: 2.4–2.8

Hardness: 5
Color: Translucent white/clear (frosted)
Luster: Vitreous to waxy/frosted

Identified March 22, 2026More man-made material (anthropogenic 'mineraloid') →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed from discarded glass bottles or jars that have been physically weathered and chemically hydrated by ocean or lake water over several decades. Most sea glass is 20 to 100 years old.

Uses & applications

Primarily used in jewelry (necklaces, earrings), mosaic art, home decor, and as a popular beachcombing collectible.

Geological facts

A piece of glass must tumble in the water for at least 20 to 30 years to develop its characteristic frosted texture and rounded edges. Historically, 'Genuine' sea glass is becoming rarer as plastic replaces glass containers.

Field identification & locations

Identify in the field by its rounded, non-sharp edges and 'frosted' pitting on the surface. Found on rocky or pebbly shorelines near historical dumping sites or high shipping traffic. Authentic pieces will have tiny 'C' shaped hydration marks under magnification.

Other man-made material (anthropogenic 'mineraloid') specimens

See all

Asphalt Concrete (Bituminous Conglomerate)

Anthropogenic Bituminous Conglomerate

sedimentary

Cullet (Slag Glass)

Amorphous Silica (SiO2) with various metal oxide colorants

mineraloid / anthropogenic

Concrete with Exposed Aggregate

Anthropogenic conglomerate (Concrete)

man-made rock (sedimentary analogue)

Concrete / Anthropogenic Conglomerate

Man-made composite material (Portland cement, aggregate, and water)

not a natural rock

Lava Rock with Fabric Impression

Scoria or Basalt with anthropogenic impressions

igneous

Green Slag

Anthropogenic Silicate Glass

Mineraloid (Industrial byproduct)