When it comes to choosing the best pick among Gems for Gemini gemstones, Apatite is known to be a popular choice!Physical properties of Apatite include its hardness, gravity, fracture, cleavage, etc. For any gemstone crystal, Apatite Optical Properties are responsible for imparting various physical properties to its structure. Knowledge of these properties is equally important to gem-cutters as well as to consumers. Apatite cleavage is nothing but the plane across which the crystal splits during cutting. Apatite cleavage is  indistinct,  indistinct,and specific gravity of Apatite is 3.16-3.23.
The physical properties of Apatite, in fact, are imparted by the chemical composition of its individual molecule. The reactivity or inertness of the crystal is solely governed by its chemical structure. Chemical composition of Apatite is represented by Ca 5(PO 4) 3(F,OH,Cl)Walter Schumann , Gemstones of the world (2001) More from other references.