mineral

Rough Gemstone Grains (Mixed Sapphires and Quartz)

Corundum (Al2O3) and Quartz (SiO2)

Hardness: 7 (Quartz) to 9 (Sapphire) on Mohs scale. Colors: range from clear, yellow, pink, and dark blue. Luster: Vitreous. Crystal structure: Hexagonal/Trigonal. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65 - 4.1.

Hardness: 7 (Quartz) to 9 (Sapphire) on Mohs scale
Luster: Vitreous

Identified March 21, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Usually found in alluvial or 'gem gravel' deposits where heavier, harder minerals concentrate after eroding from metamorphic or igneous host rocks like pegmatites and basalts over millions of years.

Uses & applications

Small rough grains of this size are used for gemstone 'mining' bags for tourists, craft projects, or as low-grade industrial abrasives due to high hardness.

Geological facts

Sapphire is the same mineral as Ruby (Corundum); they only differ based on the trace elements that provide color. These small 'mealy' grains are common in place deposits in regions like Montana, USA, or Sri Lanka.

Field identification & locations

Identify in the field by looking for water-worn, rounded or angular translucent pebbles in riverbeds. Collectors use screens to sift through gravel. Due to high density, they often sink to the bottom of a sifting pan.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral