Quartzite Pebble

Hardness: 7 (Mohs scale), Color: tan to light brown, Luster: dull/waxy, Crystal structure: granular/crystalline (microscopic), Cleavage: none, Specific gravity: 2.6-2.7. Extremely durable and resistant to weathering.

Formed from the metamorphism of quartz sandstone. Intense heat and pressure caused individual quartz grains to recrystallize and fuse together. The location (near the Diois/Drôme region in France) is rich in sedimentary and low-grade metamorphic rocks from the Alpine orogeny.

Commonly used in construction as crushed stone or road ballast; smaller pebbles are used for landscaping and aquariums. It has little jewelry value unless exceptionally colorful.

Quartzite is so hard that when it breaks, it fractures through the quartz grains rather than along their boundaries, unlike sandstone. The rounded shape indicates significant transport and erosion by water, likely in a riverbed or ancient glacier path.

Identify in the field by its hardness (will easily scratch glass) and lack of reaction to acid. It is ubiquitous in riverbeds of the Drôme department due to the erosion of the surrounding Alpine foothills.