Chalcedony (variations like Agate or Jasper)

Hardness: 3-4 (Mohs), Color: Variable (often grey, brown, black, white), Luster: Vitreous, Crystal structure: Crystalline aggregate, Cleavage: N/A, Specific Gravity: 2.71

Formed from silica-rich solutions, often in cavities of volcanic rocks or sedimentary environments. It precipitates from low-temperature hydrothermal fluids. Geological age is variable, ranging from relatively young to ancient depending on the specific deposit.

Widely used in jewelry (cabochons, beads), ornamental objects, carvings, and sometimes for precision components due to its hardness and uniform texture. Historically used for tools and weapons.

Geodes and thunder eggs are often partially or completely filled with chalcedony. It's often dyed vibrant colors for decorative purposes. Agate, jasper, and onyx are all varieties of chalcedony.

Commonly found in volcanic and sedimentary rocks worldwide. Look for a waxy luster and often banded or concentric patterns. It can be identified by its conchoidal fracture and its relative hardness (scratches glass). Field identification often involves looking for rounded, water-worn pebbles in riverbeds or gravels, especially in areas with volcanic or sedimentary rock outcrops.