Bannisterite grows in flat platy aggregates. It has smooth cleavages without ruling. It is a
pleochroic mineral, which is an optical phenomenon. Depending on which axis the mineral is being inspected on, it appears as it changes colors. on the x axis, the mineral is seen in a colorless to pale yellow color. Common impurities include zinc and sodium. It occurs in
sulfuric zinc deposits, as well as at silicate-carbonate hosted zinc deposits. It is associated with
quartz,
baryte,
fluorite,
rhodonite,
sphalerite,
galena,
calcite, the
apophyllite group and the
amphibole supergroup. It doesn't have luminescent properties, under long, or shortwave
ultraviolet light. It has a type locality in the
Benallt mine in Wales, United Kingdom, and in the Franklin mine, New Jersey, United States. ==References==