sedimentary

Quartz Pebble with Muscovite Mica

Quartz (SiO2) with Muscovite Mica (KAl2(AlSi3O10)(F,OH)2)

Mohs hardness of 7 (quartz body) and 2-2.5 (mica inclusion). Colors range from tan, yellowish-brown to white and clear. Glassy to greasy luster on quartz, pearly to vitreous and flaky on mica. Trigonal quartz mass with monoclinic mica flakes.

Identified July 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as a stream-rounded river cobble or beach pebble composed primarily of vein quartz, containing a small pocket or inclusion of shiny mica crystals. Shaped by hydraulic erosion over thousands to millions of years.

Uses & applications

Mainly collected as a beachcombing or rockhounding curiosity specimen. Quartz is used in glassmaking and electronics, while mica is used as an insulator and in cosmetics.

Geological facts

Quartz pebbles with exposed crystal pockets or mica flakes are often referred to as 'pocket rocks' by amateur collectors. The mica displays a silvery reflection due to its perfect basal cleavage into thin sheets.

Field identification & locations

Identified by the smooth, rounded, tan-white microcrystalline to massive quartz matrix housing a small cavity filled with bright, reflective, flaky mica flakes. Commonly found in stream beds, river gravels, and along coastlines worldwide.

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