Bisbee daily review., 1904-08-13
ORE DEPOSITS OF BISBEE
By F. C. RANSOME.

to be seen with the naked eye their presence in the altered minera,.zed limestone can generally be recogriz d by a faint greenish tint in the rock. joined with a certain compactness If texture that is unlike that fouii in any of the unaltered linn est Jnss Most of the limestone encountered in the Spray workings from the fourth slevel down. and in the Calumet & Arizona mine from the S50-foot level down. exhibits this development of tremolite and diopside. and all grad ations may be studied from lime stones, consisting almost exclusively of calcium carbonate to those in which all af the carbonic anhydride has been replaced by silica.
 A colorless garnet, probably the cal cium aluminium garnet, glossu.ari-e, occurs nsome of the altered lime stone. associated with tremolite and diopside. This mineral associated with 'tremolite, diopside and caleite. was particularly noted in the altered lime stone from the new station on the II 15ONfoot level of the Calumet & Ari zona mine (the deepest point reached i in the underground exploration of the 6istrict) and On the fifth level of the Holbrook northeast of the shaft. Quartz varys greatly in abundance in different portion of the ore-bearing ground few small veinlets of quartz, carrying pyrite. were observed in the altered limestone on the 950 foot level of the Calumet & Arizona mine but vein quartz in exceptional in connection with cupiferous ore bodies. The mineral. where it occurs at all. usually has the form of fne-grained aggregates that have replaced the cal cirm carbonate of the limestone or the feldspars of the granite-porphyry. Small amounts of quartz may be us- ually be found as microscopic con stituent associated with tremolite. diO- | side. garnet and pyrite in the altered ! limestones of the locally prevalent type Near the porphyry mass of Sacramento hill quartz is more abund- ant than elsewhere. Much of the rock | in the vicinity of the Gardner shaft for example originally limestone. now consists essentially of finely crys- talline granular aggregate of quartz with varying amounts of pyrite and chlorite. The bottom of the shaft at the time of the visit was in such material. Quartz of the same fine grained granular character associated with pyrite sericite and kaolin also makes up much of the altered and min eralized granite-porphyry of Sacramen- to hill.
 On the S00-foot level of the Lowell mine the greater part of the west drift is in a mass of loosely coherent pulverulent silica much of which, when dry runs like sand. This ma terial is associated ws.h some vel low clay. little decomposed porphyry and occasional punches of oxidized ore Embedded in the sandy mater ial are occasional very irregular hard CT masses composed of finely granular quartz. These are cavernous and drusy on their peripheries adn lie in the loose siliceous powder much like Hints in chalk. The microscope shows that the pulverulent silica is composed of grains which are neither rounded by attrition nor yet bounded by crystal planes. They are rough in outline showing either that they have undergone corrosion or formed part of a fne-grained aggregate from which some more soluble constituent has been removed. It is probable that this saccharidal quartz repre- sents a zone of Assuring and breccia- ton in the limestone, along with some silicifcation took place. The calcium carbonate. of the shattered partly silicifed limestone was then dissolved away leaving the quartz in it's in coherent condition.
 Most of the soft, earthly oxidized ores mined in the Copper Queen and Calumet & Arizona mines are accom- panied by and more or less intimate ly mingled with imonite and clays of various colors. The limonite some times occurs in stalactitic or botry- oidal form, but in the present work ings is more often earthly and mixed with ore or clay.
 The clay is sometimes white, some times pink or greenish-gray, but more often it is yellow or reddish from the presence of limonite. A snow-white waxy variety, beautifully. diversified by little veinlets of hght-green mala- chite, was collected on the second level of the Copper Queen mine about 250 feet south of the Holbrook shaft, and subjected to chemical examina. ton as representative of the purest form in which these clay-like second ary products occur.
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