The specimen which is the subject of the present note consists of a group of large rude, reddish crystals of tetrahedral aspect, which in colour, lustre, and general appearance, resemble garnet; they were formerly supposed to be garnet pseudomorphous after some tetrahedral mineral, and the original mineral was presumed to have been fablerz, on account of the size of the crystals, which measure as much as 3 to 5 centimetres across.