The mineral keeleyite, a sulphosalt of lead from the Oruro district of Bolivia, was originally described by Mr. S. G. Gordon2 as a new species having the formula 2PbS ·3Sb2S3. The first analysis, which was made by Whitfield, was corrected on the assumption that the contaminating sulphide was principally chalcopyrite. Later it was found that the so-called chalcopyrite was in reality stannite. The first formula as above deduced was 2PbS·3Sb2S3. Since the tin present would be included and weighed with the antimony, there was opportunity for a considerable error in the important relation existing between basic and acid sulphides in the compound, and some doubt was entertained as to the correctness of the formula derived for the mineral. Some reviewers questioned the validity of the mineral as a distinct species and, in fact, one of the present writers allowed a review of the original description to be published over his name (E.V.S.)3 questioning the reliability of the formula adduced. In a commendable effort to further establish or discredit his species, Mr. Gordon has encouraged and assisted continued work on this mineral. The single original specimen, measuring 3×5×7 inches4 was not obtained in place but was found on the cancha of the San José mine at Oruro. Mr. Gordon had hoped, on his second visit to Bolivia in 1925, to obtain more material for a more thorough and extended investigation of the mineral. As these hopes were not realized, a new analysis and mineralographic examination was made on the original specimen.

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