June, ~92o.] U . S . BUREAU OF MINES NOTES. 795

M I N I N G A N D P R E P A R I N G D O M E S T I C G R A P H I T E FOR

CRUCIBLE USE.

By Geo. D. Dub and F. G. Moses.

BE~.ORE I9I 5 nearlv all the graphite used in crucible manu- facture in the United States was imported, the small domestic output being used for lub.ricants, paints, foundry facings, and other purposes, but the combination of large demand for crucibles and the short life of crucibles made from other than the Klinge~- berg clay, no longer attainable:, lead to its use in greatly increased qnantities. The War Industries Board finally ruled that ~2o per cent. domestic flake graphite should be used in crucible mixture during I918 and 25 per cent. during I9I 9. Alabama, New York, Pennsylvania and Texas were the principal producing states, there being thirty-nine plants in three counties of Alabama. New York, which for many years had been the principal source of domestic production, had only three mines in operation in I918, having yielded first place to Alabama. In Pennsylvania five plants were in operation in Chester County. While in Texas, three properties were active, in I918 , in the central region hetweetl Llano and Burnet. Details as to these operations, methods of concentration of the ores, the preparation of domestic graphite for crucible use, are given in Bulletin I I2 of the Bureau of Mines. The method of rapid analysis of graphite used b,y the Bureau of Mines is also described. There are four methods of concentrating graphite ores, water " skirt flotation,"' the pneu- matic process, the log,-washer process, and oil-froth flotation. The product of the first concentration is a comparatively low- grade concentrate. The second step,, finishing, as it is called, is much more difficult to carry out, and is the one that demands the greatest amo,unt of investigation and improvement. Much experimental work on the preparation of Alabama graphite was carried on at the Salt Lake City station of the Bureau of Mines l~.y F. G. Moses. The whole success of a finishing process depends on the removal of a large percentage, of coarse hard impurities that tend to cause excessive destruction of valuable flake in the buhr-mill grinding. Details as to the investigations and the processes recommended are given in the bulletin of the Bureau of Mines already referred to.