Obsidian and Gypsum Physical Properties
Tenacity
Not Available
  
Flexible
  
Solubility
Not Available
  
Soluble
  
Durability
Not Available
  
Not Available
  
Specific Gravity
2.35-2.60
  
2.20-2.40
  
Fracture
Conchoidal, ConchoidalWalter Schumann, Conchoidal
  
Conchoidal, Splintery, Fibrous, UnevenArthur Thomas, Gemstones (2009)
  
Cleavage
Not Available
  
Perfect on {010}, distinct on {100}
  
Mohs Hardness
5-5.5
  
2
  
Chemical Composition
Not Available
  
CaSO 4 -2(H 2O)Arthur Thomas , Gemstones (2009)
  
Obsidian and Gypsum Chemical Formula
While comparing Obsidian and Gypsum physical properties, the important data you should know is its chemical composition. Since chemical formula defines the molecular structure of the crystal, most of the physical properties like color, tenacity, solubility are governed by Obsidian and Gypsum chemical formula.
>- Chemical formula of Gypsum- CaSO 4 -2(H 2O)Arthur Thomas , Gemstones (2009)
Obsidian and Gypsum Specific Gravity
Another important criteria for qualitative analysis of gemstones is Obsidian and Gypsum Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Obsidian and Gypsum Optical Properties during the identification of gemstone. Specific gravity of Obsidian is 2.20-2.40 whereas that of Gypsum is 2.20-2.40.