Hyalophane or jaloallofane is a crystalline mineral, part of the feldspar. It is considered a barium-rich potassium feldspar. Its chemical formula is (K,Ba)[Al(Si,Al)Si 2O 8], and it has a hardness of 6 to 6 1⁄2. The name hyalophane comes from the Greek hyalos, meaning "glass", and phanos meaning "to appear".
An occurrence of hyalophane was discovered in 1855 in Lengenbach Quarry, Imfield, Binn valley, municipality of Binn, Canton of Valais, Switzerland. The mineral is found predominantly in Europe , Bosnia , New Jersey Hyalophane may be found in manganese
Hyalophane has a monoclinic crystallography, b = 12.95 Å, c = 7.14 Å, and β = 116°. Optically, the material exhibits biaxial birefringence values of nα = 1.542, nβ = 1.545, and nγ = 1.547 and a maximum birefringence of δ = 0.005. It has weak dispersion and low surface relief.
Hyalophane has sometimes been used as a gemstone