formation is a destructive, rather than a constructive factor in oil accumulation. CONCLUSIONS. The foregoing notes lead to the following conclusions in so far as the Pennsylvania and Oklahoma regions are concerned: I. Oil has been forced out of the fine bituminous shales by the capillary action of water. 2. The oil has accumulated in nearby porous beds either by the porous bed or beds being in direct contact with the source of supply or by fracturing, as suggested by McCoy, if the two are not in contact. 3. No wide lateral movement of oil has taken place and the present position and shape of oil pools closely conforms to the underlying or overlying source of supply. 4. The areas of supply are lagoonal areas close to and generally parallel with the coast line at the time of deposition. 5. Pools generally occur in alignment corresponding to the coastal lagoonal areas, each line of pools corresponding to succesive shore lines, with generally barren belts intervening. 6. Larger pools are elongated to correspond to the prevailing elongation of the larger basins of accumulation. 7. Certain types of structure are favorable for large initial yield of oil, since domes, if they happen to exist in a productive area, act as pressure traps for gas. 8. Oil pools, in Pennsylvania and Oklahoma, may be largely of pre-deformational accumulation. 9. A detailed study of paleography and a delineation of ancient shore lines would prove of considerable value in directing the major drilling developments. 10. There may be extensive areas of favorable oil land in regions condemned at present because of the lack of so-called favorable structure.. MASSACHUSETTS INSTITUTE OF TECHNOLOGY, THE OCCURRENCE OF BINDHIEMITE AS AN ORE MINERAL.1 EARL V. SHANNON. Bindhiemite, a hydrous antimonate of lead of somewhat variable composition has commonly been regarded as a comparatively rare mineral. For some time past, the writer has been engaged at intervals in the examination of specimens of this mineral with a view to learning definitely its mineralogical nature and chemical composition. Results of analyses seem to indicate that there may be two minerals included under the name bindhiemite but discussion of the constitution of the species will be reserved for a more strictly mineralogical paper to be published in the Proceedings of the U. S. National Museum. The investigations have shown bindhiemite to be much more common than is generally believed and its widespread occurrence in oxidized lead-silver deposits of the western states is worthy of some attention from students interested in the chemistry of oxidation and secondary enrichment. Below are given descriptions of bindhiemite bearing ores from a number of new localities, with references to those previously described. In the Coeur d'Alene District, Idaho, great bodies of oxidized ore have been mined from the upper portions of silver-lead veins in quartzite. The oxidized ores consisted for the most part of cerussite and limonite with smaller amounts of anglesite, pyromorphite, plattnerite, and native silver. A common constituent of the oxidized ores of all of the larger mines of the region was a soft, ocherous material of a canary yellow color, which except in its brighter tone of color, looked very much like the ocherous limonite which was very abundant in the ores. The miners recognized this mineral and commonly referred to it as "chlorides" and 1 Published from the Division Applied Geology, U. S. National Museum, by permission of the Secretary of the Smithsonian Institution. regarded it as indicating rich silver values in the oxidized ore. Such soft yellow material was recognized by Ransome and described as massicot.2 The present writer made some preliminary blowpipe tests on this material and obtained no distinctive reactions for antimony, which results led to the statement in an earlier paper3 that bindhiemite did not occur. Later more thorough examination established the presence of antimony in all specimens of this yellow substance from every oxidized ore body in the district. No specimen of genuine massiot is now known to have been found in the region. In the Caledonia, Hercules, and Mammoth mines, hundreds of tons of ores in which bindhiemite was a conspicuous constituent have been mined, and in much of the ore of the Caledonia mine the valuable metals were contained in this mineral alone, masses of nearly pure bindhiemite several feet in diameter at times being exposed in the oxidized ores and having the same position and attitude as masses of tetrahedrite in the unoxidized portions of the vein. Sulphantimonites other than tetrahedrite are rare in this district and the bindhiemite seems to represent a pseudomorph in most cases after tetrahedrite and to have formed by reaction between lead compounds in solution and the antimonial mineral in place. That a reversal of this relationship is possible is shown by occasional masses of galena crusted with bindhiemite and by masses of bindhiemite having the granular structure and cubic cleavage of galena preserved. The mineral has been especially prominent also in ores of the Last Chance, Sierra Nevada, Blackbear, Poorman, Morning and numerous other mines in this district. The material usually is a little less rich in silver than the tetrahedrite of the same mine. In the Hypotheek mine the bindhiemite is derived from a silver-free famatinite and carries little silver. A specimen of earthy compact bindhiemite of a bright yellow color associated with limonite and cerussite from this mine, upon analysis yielded the following results: 2 Ransome, F. L., and Calkins, F. C., "Geology and Ore Deposits of the Coeur d'Alene Mining District, Idaho," Prof. Paper U. S. G. S. No. 62, p. 94. 8 Shannon, E. V., "Secondary Enrichment in the Caledonia Mine, Coeur d'Alene District, Idaho," ECON. GEOL., vol. VIII., No. 6, September, 1913, p. 565. The above analysis may be interpreted as a mixture of the following mineralogical composition: Ocherous yellow bindhiemite carrying considerable values in gold occurs at the Loxley mine, South Mountain Dist., Owyhee Co., Ida. At a small mine near Boundary, Wash., lumps of a mineral resembling tetrahedrite occur surrounded by a crust of earthy yellow bindhiemite, imbedded in coarse galena. In the Elkhorn district, Mont., bindhiemite occurs sparingly with cerussite and calamine in oxidized ores of the Elkhorn mine. Ocherous bindhiemite occurs with galena cerussite and anglesite in quartz from the Modoc Chief Mine, Boulder District, Jefferson Co., Montana. In South Dakota, ocherous bindhiemite occurs sparingly in auriferous quartz ore at the Durango mine, at Lead, Lawrence County. Specimens from Silver City show compact wax-like yellow to brown bindhiemite with a fibrous structure suggesting silicified wood, the structure being pseudomorphous after jamesonite from which the bindhiemite is derived. In Utah bindhiemite occurs abundantly in the Park City district as a yellow to greenish impure alteration product of tetrahedrite as described by Boutwell. Ordinary ocherous yellow 4 Boutwell, J. M., "Geology and Ore Deposits of the Park City District, Utah," Prof. Paper U. S. G. S. No. 77, pp. 110-114, 1912. bindhiemite occurs with impure cerussite at the Eureka Consolidated mine, Tintic District; coating galena at the Crescent mine, Gate Co.; Niantic Mine, Lucin Dist., Boxelder Co., with cerussite; Flavilla mine, Dry Canon Dist., Boxelder Co., with galena and linarite; and at the Hornsilver Mine, San Francisco District with cerussite. In Nevada bindhiemite is of very widespread occurrence. Compact yellow lead antimonate occurs with galena, tetrahedrite, and malachite in ores of the Belmont and Highbridge mines, Philadelphia District, Nye Co. A red ocherous material from the Wamsley Mine, Mineral County, upon analysis yielded the following results: The material is so fine grained as to appear homogeneous under the microscope. It seems not improbable that this peculiar mixture resulted from the oxidation of the mercurial variety of tetrahedrite. Analyses of three yellow bindhiemites from the same locality are given in the following table: |