"Store Didoni" Collection, Macherio (MB)

Typically found in India (Gujarat, Ratanpur district), Brazil, and Uruguay, it is a variety of chalcedony whose orange-red color is due to iron oxide (hematite) inclusions dispersed throughout its fibrous microcrystalline structure. It forms through the cyclic precipitation of colloidal silica in cavities within volcanic rocks; most of the carnelian on the market undergoes heat treatment (approximately 400–500°C) to intensify the red coloration of paler or yellowish raw material, a practice that has been widespread since ancient times. Hardness 6.5–7 on the Mohs scale, density 2.6 g/cm³.

Used since ancient Egypt and Mesopotamia for seals, amulets, and jewelry; widely used today in cups, plates, and fine carved objects; valued in crystal therapy as a stone of energy and vitality.