Pic Description: Onyx is generally translucent to opaque, hardness 6.5 to 7 degrees, the proportion of 2.55 to 2.91, refractive index 1.535 to 1.539. Agate very distant history, it is the earliest human use of gem material. Agate agate water tank is the most valuable species, characterized by closure of the hole in agate which contains water.
