Jasper

Jasper is an opaque, impure variety of microcrystalline quartz that gets its wide range of colors and patterns from mineral inclusions - primarily iron oxides, clay minerals, and organic matter. It forms through silicification, where silica-rich fluids permeate and replace existing rocks or sediments.

The incredible diversity of jasper patterns reflects the diversity of formation environments. Picture jasper from Oregon preserves ancient landscapes in stone - the patterns are actual cross-sections of volcanic ash deposits, each colored band representing a different eruption. Ocean jasper from Madagascar forms in volcanic rock with distinctive orbicular (circular) patterns created by radial crystal growth. Mookaite from Australia is a biogenic jasper formed from the silicified remains of microscopic marine organisms (radiolaria).

This variety makes jasper one of the most collectible mineral groups - each locality produces patterns and colors found nowhere else, and new varieties continue to be discovered and named.

Jasper is defined by being opaque microcrystalline quartz - this distinguishes it from agate (translucent, banded), carnelian (translucent, orange), and chalcedony (translucent, various colors). At Mohs 7, it's hard and durable with a waxy luster.

Identifying specific jasper varieties requires familiarity with locality-specific patterns. The fracture is typically smooth to splintery. Jasper does not fluoresce. In thin section under a microscope, it shows a granular texture of interlocking quartz microcrystals.