Today, one of the world's acknowledged mineral rarities, though it used to be collected a long time ago from overgrown pit heaps by the inhabitants of Kutna Hora
. It was used for poisoning fieldmice and other field vermin. This poisonous clay, known also by the place name of its discovery, 'clay of Kutna Hora', was widely known and it was considered to be 'arsenic' (arsenic trioxide). In 1901 Antonin Bukovsky
, a Bohemian
chemist, who studied minerals of old pit heaps, proved it was an arsenate.
Bukovskyite forms nodules with a reniform surface, which under a microscope appear as a collection of minute needles similar to gypsum. Some can be seen with the naked eye and occur inside the nodules. Bukovskyite has so far only been found in one locality of the world, on pit heaps from the Middle Ages, where sulphate ores had been mined at Kank, north of Kutna Hora and other old deposits in the vicinity. As it has only recently been defined and acknowledged, it has attracted great attention from mineralogists and collectors. This is because it is one of the few newly discovered minerals which occur also in fairly large, and fairly conspicuous pieces. One must handle it with care, however, for it is a highly poisonous mineral.