Granitoid Pebble (Graphic Granite/Pegmatite)

Physical Properties

Hardness: 6-7 Mohs; Color: Tan, cream, and grey; Luster: Vitreous to pearly; Structure: Phaneritic (coarse-grained); Cleavage: Perfect in two directions (feldspar) and none (quartz); Specific gravity: 2.6-2.7.

Formation & Geological History

Formed from the slow cooling of silica-rich magma deep within the Earth's crust, typically during the final stages of crystallization where mineral growth is enhanced. This specimen shows water-worn rounding, likely from a river or beach environment.

Uses & Applications

Large deposits are used for architectural stone and countertops. Small pebbles like this are collected as decorative stones or used in landscaping.

Geological Facts

The interlocking texture of dark quartz and light feldspar seen in similar specimens is often called 'graphic granite' because it resembles ancient cuneiform or runic writing.

Field Identification & Locations

Identify by looking for the distinct mixture of translucent quartz and opaque pinkish or tan feldspar. It will be very hard (cannot be scratched by a steel knife) and often found in glacial till, riverbeds, and mountainous regions.

Identified on: 4/28/2026

Mode: Standard