The chemical formula of Celsian is indicated by BaAl2Si2O8 or Barium Aluminum Silicate. Celsian belongs to the Silicates Group of minerals. It is sometimes found with some calcium and potassium. Celsian is usually found forming a solid solution series with Orthoclase and the intermediary member is hyalophane. Celsian is most commonly found colorless, white, light yellow, reddish, brownand sometimes gray, all of which can be very interesting and fascinating when evaluated or viewed with the aid of petrographic polarizing light microscope used in optical mineralogy. Celsian is most commonly found leaving a white streak when rubbed on a white porcelain streak plate. The hardness measure of Celsian is only 0.5 and it is usually found occurring in short tabular crystals and long slender prisms. It is actually known to crystallize in the monoclinic system of crystal formation. In optical mineralogy, the monoclinic system of crystal formation comprises crystals having three axes of unequal lengths. Two of which are usually found in a position that is oblique or not perpendicular to one another. However, both of which are commonly found perpendicular to the third axis. Celsian also occurs acicular and massive in form. The specific gravity measure of the mineral is usually ranging from 3.1 to 3.4 grams per cubic centimeters. It is usually found showing a vitreous to greasy luster when viewed in reflected light of polarized microscope used in optical mineralogy.             Celsian is commonly found having basal, prismatic and pinacoidal cleavages when closely evaluated under polarizing microscope on optical mineralogy. The cleavages are actually found at an angle of about 90-degree. Celsian is known to have conchoidal to uneven fracture when viewed in petrographic polarizing microscopes. It also shows brittle tenacity. Celsian is polymorphous with another interesting mineral called Paracelsian. Paracelsian is known as the orthorhombic form of Celsian mineral.  The striking features of Celsian include its heaviness, crystal forms and hardness. Celsian is known to be soluble in hydrochloric acid. Celsian is usually associated with aragonite, quartz, barite and other plagioclase feldspars. Celsian notably occurs at several localities including Swuitzerland, Wales, Italy, Sweden, Japan, Namibia and Australia.