The Keystone Gold Mine, owned in Portland, is situated seven miles north of Prairie City, in Grant County. It is the most important property in this (Quartzburg) district. It comprises three claims, and has a continuous length of forty-five hundred feet. The quartz carries free gold, metallic silver, iron and copper pyrites, zinc blende, and galena. Assays show one hundred and six dollars per ton in gold, and from one hundred dollars to one thousand dollars in silver. The property is valued at fifty thousand dollars.
The Pine Creek mines, of which one hears a good deal, are situated near the Snake River boundary of Union County, and are geologically interesting, as the stream on which they are situated rises in rugged peaks of greater elevation than any other in the Blue Range. The geology of the district is clearly seen in the canons of Pine Creek, which show that the foundation of this region is granite overlaid by slate, which, when the internal heat of some volcanic period had fused the granite, was lifted up, broken, and thousands of its fissures filled with the molten rock, by which means the eccentric granite dikes of the district were formed. Other fissures were opened, cutting the granite, which gradually filled with mineral solutions carrying quartz, iron pyrites, copper, galena, and, in smaller proportions, gold and silver. At some later period other convulsions followed, during which dikes of lava, trachytic or porphyritic in character, were forced up through the strata, cutting the quartz veins. At a still later period there was an outburst of melted trap rock, which filled deep fissures, and cooled in thick sheets over all. Water and ice wore away this covering forming the soil of East Oregon, as previously noted, and also in carving out the perpendicular dikes left cavernous recesses in the cliff’s, but the lava dikes were left standing like monuments to the dead granite and trap.
It is superfluous to remark that where successive meltings and upheavals have occurred the quartz veins in the older granite are often interrupted and lost, and that no miner is safe from such an ending to his enterprise. Nevertheless, the Pine Creek mines enjoy a high reputation.
About 1862 some Umatilla Indians brought a quantity of gold, which appeared to have been extracted from quartz in an im-
