Microcline var. Hyalophane

Hyalophane is a clear and colourless variety of Microcline Feldspar, deriving its name from the Greek meaning to “appear like glass”.  The mines within the district of Busovača in the Central Bosnia Canton of Bosnia and Herzegovina, are known to produce excellent Hyalophane specimens and this is no exception.  A large 5.0 x 5.0 x 3.8 cm crystal comprises the bulk of this small cabinet specimen, attached at one side to iron-stained Quartz on top of which is a nicely terminated 2 cm long Smoky Quartz crystal.  The Hyalophane at one side appears to form a chevroned twinned crystal, clearly indicated by re-entrant faces and a divide in colour along the twinning plane.  The bulk of the Hyalophane is transparent grading to gemmy, although internal feathers, clouds and veils constantly interrupt its optical properties.  This is a showy example of Hyalophane enhanced even more by the Smoky Quartz crystal.  I suspected this would fluoresce well in ultraviolet light, but there is no response in either long or short wave.