Quartzite (specifically an iron-stained or Carnelian-colored variety)

Physical Properties

Hardness: 7 on Mohs scale; Color: Orange-peach to reddish-tan; Luster: Vitreous to waxy (when polished); Crystal structure: Hexagonal/Trigonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.65.

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. High heat and pressure reciprocal to tectonic processes fuse individual sand grains into a solid crystalline rock. The orange hue is typically caused by the oxidation of iron minerals (limonite or hematite) within the matrix.

Uses & Applications

Commonly used as decorative gravel, in landscaping, and as a tumbling stone for beginner collectors. High-quality pieces are used in jewelry as beads or cabochons. Industrially, it can be a source of silica for glass manufacturing.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rock layers, leading to the formation of prominent ridges and peaks in mountain ranges. This specific specimen has been water-worn and smoothed, likely in a river or a beach environment.

Field Identification & Locations

Identify in the field by its hardness (it will easily scratch glass) and its sugary texture under magnification. Unlike marble, it will not react or fizz when exposed to acid (vinegar/HCl). Found worldwide in ancient mountain belts.

Identified on: 4/27/2026

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