mineral
Polished brown jasper or chert pebble
Microcrystalline quartz (SiO₂), likely iron-stained chalcedony/jasper
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; dark brown to black with rusty-gold mottling, a smooth waxy to subvitreous luster, and no visible cleavage. The rounded shape indicates water tumbling or deliberate polishing; density is typically about 2.6 g/cm³.
Identified More mineral →
Explore Polished brown jasper or chert pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness about 6.5–7 Mohs; dark brown to black with rusty-gold mottling, a smooth waxy to subvitreous luster, and no visible cleavage. The rounded shape indicates water tumbling or deliberate polishing; density is typically about 2.6 g/cm³.
Formation & geological history
Silica-rich groundwater replaced or cemented fine-grained sediments, with iron oxides producing the brown coloration; formation may span millions to hundreds of millions of years. The present pebble shape likely developed in a stream, beach, or tumbler.
Uses & applications
Used for cabochons, beads, carvings, decorative stones, and lapidary practice; attractive examples are collectible but generally inexpensive.
Geological facts
Jasper and chert are opaque varieties of microcrystalline quartz and can be difficult to distinguish visually from one another without examining texture and translucency.
Field identification & locations
Look for quartz-like hardness: it should scratch ordinary glass, while a steel blade usually does not scratch it easily. Common sources include river gravels and silica-rich volcanic or sedimentary terrains worldwide; exact locality cannot be determined from the image.
