mineralogy-gemmology
Qu’est-ce que le jade des Neuf Dragons? — Enquê...
Jade des Neuf Dragons (Hua’an Yu) : enquête gemmologique, historique d’un jade culturel chinois.
Qu’est-ce que le jade des Neuf Dragons? — Enquê...
Jade des Neuf Dragons (Hua’an Yu) : enquête gemmologique, historique d’un jade culturel chinois.
Obsidian, formation, history, deposits, use, co...
Chemical formula : 70–75% SiO2, plus MgO, Fe3O4 (composed mainly of silicon dioxide) Crystal system: amorphous Density: 2.25 to 2.40 Hardness (Mohs scale): 5 to 5.5 Refractive index: 1.480 to 1.500...
Obsidian, formation, history, deposits, use, co...
Chemical formula : 70–75% SiO2, plus MgO, Fe3O4 (composed mainly of silicon dioxide) Crystal system: amorphous Density: 2.25 to 2.40 Hardness (Mohs scale): 5 to 5.5 Refractive index: 1.480 to 1.500...