Celsian: Gemstone Information 

Typically found in medium-grade contact or regionally metamorphosed rocks with significant barium particularly associated with manganese deposits. In barite-carbonate veins. Rare in igneous rocks. Localities include Broken Hill, N.S.W., Australia. Alaska range, Alaska, U.S.A. Otjosondu, Namibia. Benallt manganese mine, Rhiw, LLeyn Peninsula, Caernarvonshire, U.K. Jakobsberg, Sweden. Kaso mine, Totiki Pref. Japan and Zamora, Spain.
Appearance
Transparent to translucent. Forms short prismatic crystals; also massive. Twinning is very common.
• Lustre: Vitreous
• Colour: Colourless, white, pale yellow and yellow.
Properties
• Crystal system: Monoclinic
• Refractive index: α 1.580–1.589; β 1.583–1.593; γ 1.586–1.599 Biaxial +ve
• Birefringence: 0.009–0.011
• Density: 3.10–3.39
• Hardness: 6–6.5
• Cleavage/fracture: In two prismatic directions ranging from perfect to good. Fracture is uneven, very brittle producing uneven fragments
• Fluorescence: Non-fluorescent
• Simulant: The color of some transparent iridescent yellowish Czech glass beads has been called ‘celsian’.