Quartz

Hardness: 7 (Mohs scale), Color: Colorless to greyish-blue tinted, Luster: Vitreous (glassy), Crystal Structure: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Quartz forms in a wide variety of environments, most commonly from the cooling of magma or by precipitation from hydrothermal veins. It is a major component of igneous rocks like granite and metamorphic rocks like quartzite. The region near 43.5°N, 6.5°E (Provence-Alpes-Côte d'Azur, France) features complex geology including the crystalline Massif des Maures where quartz veins are common.

Used in glassmaking, electronics (piezoelectric properties), abrasives, construction as an aggregate, and as a gemstone or decorative mineral for collectors.

Quartz is the second most abundant mineral in Earth's continental crust. Its name comes from the German word 'Quarz', which was first recorded in 1530. It has been used since antiquity in jewelry and hardstone carving.

Identify in the field by its hardness (will scratch glass/steel), lack of cleavage, and glassy conchoidal (shell-like) fracture surfaces. It is ubiquitous in the French Riviera hinterlands, particularly in riverbeds and eroded mountain slopes.