Agostino

Mine, Inactive

Alternative names

Barnes Property
Monarch Mining Co.
Crow Creek Mining Co.

Commodities and mineralogy

Main commodities Au
Other commodities Ag; Cu; Mo; Pb; Zn
Ore minerals argentiferous galena; arsenopyrite; chalcopyrite; gold; molybdenite; pyrite; pyrrhotite; silver; sphalerite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale AN
Quadrangle map, 1:63,360-scale A-6
Latitude 61.047
Longitude -149.11
Nearby scientific data Find additional scientific data near this location
Location and accuracy Located on east side of Crow Creek about 0.7 miles south of VABM Pass (Crow Pass), mine is marked with the westernmost adit symbol on Jewell Mountain in the Anchorage A-6 1:63,360-scale map. Locality 53 of Cobb (1972) and locality 42 of MacKevett and Holloway (1977). Accurate within 400 ft.

Geologic setting

Geologic description

Park (1933) decribed the geology: Two quartz veins (called the North vein and the South vein by the owners) cut Late Cretaceous age metasedimentary rocks of the Valdez Group which are intruded by many dikes and small, irregular shaped intrusive bodies of holocrystalline argillically altered quartz diorite. Locally, the bedded rocks strike nearly west and dip 40 N. The country rock has been badly shattered near the veins, and part of the deformation is postmineral, resulting in brecciated vein materials, which in some places have been recemented and again fractured. Both the North and the South veins are traceable for several hundred feet along strike. The South quartz vein ranges in width from 6 inches to about 4 feet, with an average of 9 inches in the tunnel. The strike is from east to S 80 E, and the dip is 55 to 70 N. Many fragments of country rock are isolated in the quartz. The North quartz vein strikes N 80 E, and dips about 70 N. Where exposed in the tunnel and in several surface cuts it is from 10 inches to 3 feet wide, with an average of 1 foot. The North vein appears to be somewhat better defined than the South vein and may be traced farther on the surface. There are several crosscutting veins 6 inches wide that strike a few degrees west of north and dip either east or west. The North vein offsets these small veins. The crosscutting veins of this north-south system are very persistent and one mineralized vein 6 to 8 inches wide was followed for more than 500 feet. The mineralization includes at least two generations of quartz, small amounts of calcite, galena, arsenopyrite, sphalerite, chalcopyrite, pyrrhotite, molybdenite, pyrite, gold, and silver. The silver occurs alloyed with gold (75 percent Au, 25 percent Ag). When not with gold, the silver seems to be associated with galena. Considerable magnetite is found in the concentrates obtained by panning.
A random samples of molybdenum-bearing cross-vein contained 0.26 percent Mo (Park, 1933). Samples taken by the Bureau of Mines contained up to 234 ppm Au and 92 ppm Ag (Hoekzema and others, 1987). Jansons and others (1984) report 43 chip and grab samples contained from a trace to 6.82 oz/ton Au, trace to 3.94 oz/ton Ag, up to 400 ppm Mo, and 1.34 percent As. Weighted average grade of all chip samples is 0.31 oz/ton Au and 0.31 oz/ton Ag.
Geologic map unit (-149.112188991518, 61.0464356923095)
Mineral deposit model Chugach-type low-sulfide Au-quartz veins (Bliss, 1992; model 36a.1).
Mineral deposit model number 36a.1
Age of mineralization Tertiary or younger.
Alteration of deposit The intrusive rocks have undergone argillic alteration. Some galena has been altered to cerussite (Johnson, 1912). Limonite and abundant scorodite is also present where arsenopyrite is prominent (Hoekzema and other, 1987).

Production and reserves

Workings or exploration
Berg and Cobb (1967) indicated the Agostino Mine was the site of the most extensive development in the Girdwood area. The site was discovered by Conrad Hores in 1909 and prospected or mined (with interruptions) until as recently as 1941. Johnson (1912) reports that development began in 1910. In 1910-11 there were about 675 feet of underground workings on three levels and some open cuts. Owners reported that the free milling ore from main veins averaged $35 to $40 per ton (gold at $20.67/ton), with much higher assays from single samples. Wall rocks were said to not be gold-bearing. After 1911, Brooks (1922) reported plans for some work in 1920 and Smith (1929) reported plans for adding machinery in 1926. Minor production occurred in 1926 and 1928 using a 1-stamp mill, small crusher, and amalgamation plate. Park (1933) indicated the group of claims was originally known as the Barnes property and has changed owners several times. The Monarch Mining Co obtained control several years prior to 1933. This company was taken over by the Crow Creek Mining Co., Inc. which gave a lease and option to the Bruno Agostino Mining Co. - controlled and operated by four men in partnership. The last group pushed development vigorously during 1931, installing a larger mill that utilized hydropower and three 1,200-foot tram lines (Hoekzema and others, 1987). Development of the property, 1933, included opening two parallel veins, called by the owners the North and South veins. There is one adit 260 feet long on the North vein and one 267 feet long on the South vein. In addition, there are two crosscutting adits, one containing 295 feet of workings and the other 60 feet. A lower adit, planned to crosscut the workings in depth, has been driven 190 feet. A winze on the South vein was open for 40 feet and was reported to be 10 feet deeper but filled with debris. There was also a 10-foot winze on the South vein. The total workings is 1,072 feet and the winze length more than 50 feet (Park, 1933). Production continued from 1933 until 1941. Roehm (1937) reported that development in 1937 consisted of 950 feet of drift, 125 feet of crosscuts, 52 feet of winze, and 4 raises totaling 100 feet. Two levels at elevations of 3,200 ft and 3,300 ft developed the South vein. The North vein was developed on two levels at elevations of 3,285 ft and 3,420 ft. A 60-ft-long adit was developed 500 feet north of the North vein at an elevation of 3,500 ft to examine a north-striking molybdenum-chalcopyrite-bearing vein. Most of the stoping and production appears to have come from the upper level of the south vein.
A random sample of molybdenum-bearing cross-vein contained 0.26 percent Mo (Park, 1933). Samples taken by the Bureau of Mines (Hoekzema and others, 1987) contained up to 234 ppm Au and 92 ppm Ag. Jansons and others (1984) report 43 chip and grab samples contained from a trace to 6.82 oz/ton Au, trace to 3.94 oz/ton Ag, up to 400 ppm Mo, and 1.34 percent As. Weighted average grade of all chip samples is 0.31 oz/ton Au and 0.31 oz/ton Ag. This deposit has high mineral development potential for a small mine, based on history and sampling, if vein extension can be located (Jansons and others, 1984).
Indication of production Yes; small
Production notes Total recorded production, including that of the Jewel Mine (ARDF number AN107), was 4,932 oz gold and 996 oz silver (Hoekzema and others, 1987).

Additional comments

There is some confusion in literature distinguishing between this property and the Jewel mine, which apparently was connected to Agostino mill at one time. Both were probably under the same management (Crow Creek Mining Co.) during the 1930s.

References

MRDS Number A011655

References

Reporters D.P. Bickerstaff (USGS contractor); S.W. Huss (USGS)
Last report date 7/30/1998