MISSOURI RIVER-YORK DISTRICT
Located in the southeast corner of Lewis and Clark County, on the west side of the Belt Mountains, the Missouri River-York district includes Trout Creek, York, Clark, Oregon, Cave, and Magpie Gulches - all tributaries of the Missouri River. Most of the production of this district came from placer deposits, but a significant amount came from lodes.
Placer gold was discovered in this area in 1864 about half a mile above the mouth of York Gulch (Pardee and Schrader, 1933, p. 176) ; placers along its tributaries and other streams in the district were discovered about the same time or a year or two later. Most of the placers were rich, and within a few years after discovery they were either mined out or the richest parts had been depleted and they were then abandoned. Years later some were worked by dredges, and again substantial amounts of gold were produced, especially during the periods 1909-13 and 1934-44. No placer production was reported from 1950 through 1959.
Authentic records of the early placer production of the Missouri River-York district have not been found. On the basis of the size of deposits and reported grades, the production to about 1928 of the individual deposits was estimated (Pardee and Schrader, 1933, p. 177-182) as follows:
The figures given probably should be accepted as the minimum production of these placers. Some estimates of the output of the York-Trout Creek placers alone were as high as $5 million (Pardee and Schrader, 1933, p. 176). The production of the district from 1928 through 1950 was about 41,200 ounces. The minimum placer production of the district was therefore about 265,000 ounces.
The lode deposits occur chiefly in Dry Gulch and other tributaries of Trout Creek above the old town of York. Discovery of the first lode in the district, the gold-quartz lode of the Old Amber mine, was probably made soon after mining had begun (Pardee and Schrader, 1933, p. 120), and a mill to work the ore was built before 1870. Outcrops of gold-bearing quartz, occurring mainly in shale along a dike, attracted early attention. Numerous veins along the dike were developed, and the ore was hauled to Trout Creek or other streams where it was worked in small mills and arrastres. Several mines were active between 1895 and 1900 (Pardee and Schrader, 1933, p. 121), but after 1900 all were abandoned except the Golden Messenger mine in Dry Gulch, the most productive in the district. Mining of the Golden Messenger began in 1899 (Pardee and Schrader, 1933, p. 121, 146) and continued through 1942. The lode mines were virtually idle from 1942 through 1959.
Incomplete records credit the lode mines with production worth $450,000 to $600,000, chiefly in gold, before 1932 (Pardee and Schrader, 1933, p. 121-122). Lode production from 1933 through 1943 was about 51,440 ounces, most of which came from the Golden Messenger mine. The minimum lode production of the Missouri River-York district was about 70,000 ounces. The district can thus be credited with a total gold output through 1959 of about 335,000 ounces from lodes and placers.
The area is underlain by shaly, slaty, and calcareous rocks of the Belt Series, which are folded into a large northwest-trending anticline whose northeast limb is cut by an overthrust fault. The sedimentary rocks are cut by quartz diorite dikes and stocks of Late Cretaceous or Tertiary age (Pardee and Schrader, 1933, p. 123-134).
The lodes and the placer deposits of the Missouri River-York district are closely associated with the quartz diorite dikes. Most of the lodes are small quartz veins in fractures in diorite and along the bedding planes in the adjacent shale. The veins are valuable chiefly for gold (Pardee and Schrader, 1933, p. 139-144; 147-160); silver and lead are minor constituents. The veins consist almost entirely of quartz, a little pyrite, and scattered grains of galena. The ore shoots range from a few inches to several feet in width and from a few feet to several hundred feet in length. The ore bodies in the Golden Messenger mine are irregular replacement deposits along fractures in the quartz diorite which has been altered and more or less replaced by quartz, ankerite, and small amounts of sulfides. Pyrite is the most abundant sulfide, but galena, sphalerite, and small amounts of chalcopyrite are also present. Most of the ore mined, both in the replacement shoots and in the veins, was oxidized.
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