Observations base on Obsidian
Colors: Obsidian comes in black which is it most common color for obsidian to come in, next it comes in tan or green, and for rare color that obsidian can come in is blue,red,orange, or yellow.
Hardness: The hardness of obsidian got a score out of 5 out of 10
cleavage and/or fracture: Obsidian is vitreous (like glass with appearance and physical properties)
Luster: The surface of obsidian is reflexive when light shines on the surface of obsidian.
Streak: Leaves a white crystals as the aftermath
Special properties: Obsidian can be used as mirror that's one of its special properties