A specimen in the British Museum, consisting mainly of brown chalybite and decomposed iron pyrites--the latter mostly converted into earthy oxides--bears upon its surfitce and in its cavities a number of thin prisms encrusted with a botryoidal yellowish substance which covers a great part of the decomposed specimen. On close inspection the needles are seen to be Cronstedtite, mostly but not entirely converted into black limonite, and the encrusting substance consists mainly of phosphate (with a little carbonate) of lime. The latter is sometimes crystalline on its surface.