sedimentary

Jasper or Agate Pebble

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs); Color: Mottled green, brown, and tan; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65

Hardness: 6
Color: Mottled green, brown, and tan
Luster: Waxy to vitreous

Identified June 30, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the deposition of silica from groundwater in cavities of volcanic rocks or sedimentary layers. These pebbles are typically worn smooth by fluvial or lacustrine action (river or lake wave movement). Often dates back hundreds of millions of years (e.g., Precambrian to Mesozoic).

Uses & applications

Used primarily for lapidary work, jewelry making (cabochons), fish tank decor, and as a popular collectible for beachcombers and 'rockhounds'.

Geological facts

Lake Superior is famous for its agates and jaspers, which were transported from the north by glacial movements and deposited in the lake basin and surrounding gravel pits.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and its smooth, water-worn exterior. Found along shorelines and in gravel beds. Wet the stone to see the colors and patterns more clearly.

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