Spinel and Polyhalite Physical Properties
Tenacity
Not Available
  
Brittle
  
Solubility
none
  
Soluble
  
Durability
Not Available
  
Not Available
  
Specific Gravity
3.64-3.66
  
2.78
  
Fracture
Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009)
  
Conchoidal, Brittle
  
Cleavage
None, but may exhibit slight parting
  
Perfect on {10 1 }; parting on {010}
  
Mohs Hardness
8
  
3.5
  
Chemical Composition
MgAl2O4
  
Not Available
  
Spinel and Polyhalite Chemical Formula
While comparing Spinel and Polyhalite 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 Spinel and Polyhalite chemical formula.
- Chemical formula of Spinel- MgAl2O4
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Spinel and Polyhalite Specific Gravity
Another important criteria for qualitative analysis of gemstones is Spinel and Polyhalite Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Spinel and Polyhalite Optical Properties during the identification of gemstone. Specific gravity of Spinel is 2.78 whereas that of Polyhalite is 2.78.