THE VULTURE MINE BILL FEYERABEND
OUR GOALS TONIGHT Understand a little about the geology Understand a little about the mine’s history Understand a little about changing technology Understand a little about the mine’s role in Arizona history Understand how they all tie together
Geology Now lets put all of that into a geologic context. Here is a geologic map of the Vulture mine area. Source:http://repository.azgs.az.gov/uri_gin/azgs/dlio/575
Geology That should give you a headache. Mapping at the Vullture gave me a headache until I understood the key. STRUCTURE
Geology This is critically important. The Vulture mineralization was introduced after the rocks were formed. Mineralizing fluids needed a pathway. Structures provided that pathway.
Geology Broadly, there are two styles of structural deformation: Compression which was dominant in the Mesozoic and early Tertiary time about 150 to 40 million years ago. Extension and lateral forces have dominated for about the last 40 million years.
Geology Equally broadly, there are two styles of deformation. One is under extreme pressures of miles at depth where minerals deform differently under compression.. The other is closer to the surface where the rocks are brittle and deform by brittle breaking.
Geology Lets go back and look at this image: Notice how it looks like the edge of a deck of cards: Watch this demo of applying a force to a deck of cards.
Geology At the Vulture mine, you see: A ductile zone of mid-crustal deformation. A later brittle deformation at much shallower depths along the pre-existing plane of weakness.
Geology Because we need an open plumbing system for the mineralizing fluids, we are going to begin with the extensional structural plane dipping moderately to the north. North Represent As A Plane
Geology Here we begin with that simple planar structural surface. However, it is ‘tight’ and dry.
Geology Having a brittle structural plane is not enough by itself. You have to open it so fluids can flow. There are two ways. The Vulture has both. Cross faults Warp the plane
Geology Now you apply a force down and towards the viewer on the right side of the structural plane, warping and breaking it.
Geology Now you mineralize the spaces opened by warping and breaking.
Geology After mineralization continued forces juggle and offset the mineralization along faults. Some are 10s of feet, some 100s.
Geology There is another point which favors the Vulture. Gold was deposited after sulfide minerals - like the left two slides – not with them like the right slide (more common)
Geology You can free the gold on the left by coarse crushing. You can free the gold on the right by: very expensive fine crushing roasting / smelting nature’s weathering (base of oxidation) That is why commonly pioneer mines went to base of oxidation and stopped. Vulture mine went to base of oxidation and kept going.
Geology Vertical zonation – common epithermal characteristic Little change in temp pressure when 10 miles deep Big changes when 2,000 feet deep Temp and pressure rapidly decrease Get changes in what is precipitated
Geology All of that is now dipping moderately to the north. If we go on the tour, at the overview you will be standing on chlorite schists - mid-crustal – looking down at the brittle structures hosting the mineral .
DISCOVERY Now lets switch gears from geology to history and put it in a geologic context.
Henry Wickenburg Johannes Henricus Wickenburg Born 1819 in Essen, Germany Essen is a coal mining region He mined coal with his brother on family lands.
Henry Wickenburg Emigrated to New York in 1847 and moved to San Francisco in 1853.
Henry Wickenburg 1853 in California (a little late) 1853 1862 at short lived La Paz placer gold rush 1863 1863 at Peeples Valley where Rich Hill placers 1862 just discovered
Henry Wickenburg Mining and particularly gold placer mining was a common thread t hru Henry’s life.
Henry Wickenburg Henry first saw the big white quartz outcrop in 1863 before AZ even became a territory. There was no practical way to record a claim – ownership was by possession. The location that stuck was this notice in 1864 recorded in Prescott.
Henry Wickenburg Charlie Genung put up an arrastra in June, 1864 on the Hassayampa River about 12 miles west. They recovered enough gold from the first load of rock that the race was on.
FIRST PRODUCTION The ‘big white tooth’ of quartz outcrop had dimensions of maybe 1800 feet long, 40-60 feet high and 50 feet wide. The first mining was simply quarrying of that rock mass. Soon there were tens of arrastras on the Hassayampa and several daily wagonloads carried from the mine. Henry got out of mining and into charging money. He charged $15/ton plus 1/3 of profits. Lawsuits were inevitable. At the first lawsuit in 1864, he documented income of $700/day for five months.
FIRST PRODUCTION It took about a year to quarry down the discovery outcrop. Everything about it was ideal frontier – everyman. could afford the surface quarrying and arrastra milling. Ore easily separated visually to +1 ounce Once mining started underground, the basics changed. Underground is complicated and demands capital. You had to invest money to make money.
PRODUCTION MINING – CLAIM OWNERSHIP The habits of early prospectors were to claim “feet along the lode,” so you end up with claim maps like this. The largest 600’ and the smallest were 13’ 7”.
PRODUCTION MINING – CLAIM OWNERSHIP That worked OK when quarrying a quartz hill. It does not work so well underground. Haulageways, access to pods of mineral, milling, etc are complications. Production, development, milling, exploration and financing needs put pressure for consolidation.
PRODUCTION MINING – CLAIM OWNERSHIP Beginning with the Vulture Mines Co. 1866 purchase of part of Henry’s interest, there Is a pattern of capitallized groups acquiring the Vulture, running it for a few years They always ended up done in by faults – except when done in by management. Example – the Vulture Mining Co. used geology to find the extension across the Talmadge fault in 1911 and then lost it across the Astor fault in 1916.
PRODUCTION MINING – CLAIM OWNERSHIP Not all management was an improvement. James Sexton about 1868 was named manager. He financed the mine by credit – other peoples. When mine shut down in 1872 , unpaid bills: $12,000 to store owner George Bryan $82,000 to freighter JM Bryan Time described as “contentious circumstances” Sexton returned to Connecticut and reportedly built a mansion.
PRODUCTION MINING – CLAIM OWNERSHIP Horace Tabor – Colorado silver king – leased Vulture in 1887. Defeated by faults. Lose everything in the Silver Panic of 1893 and lost Vulture to unpaid taxes. “The Vulture was my biggest mistake.”
PRODUCTION MINING – MILLING The original arrastras crushed 1-2 tons per day. Stamp mills have existed since medieval times. First stamp mill on river built in 1866. An 1869 40 stamp mill on the river crushed 80 tons per day. Stamp milling was used at Vulture into 1930s.
PRODUCTION MINING – MILLING Stamp mills required: water fuel (wood) 1880 mill paid $100-150/day ore You see variations of locating at one and bringing the other two 1879 a river – mine pipeline built 1880 End of milling on Hassayampa
PRODUCTION MINING – MILLING 1890s Cyanide first used 1930s Crushing by jaw and cone crusher, ball mill cyanide recovery using carbon
Lets recap history with a simple timeline. MINE TIMELINE 1860 Discovery, arrastras 1865 First stamp mill, Civil War ends, Malaria, Gold $50 to $28 1870 Contentious management, Fault, Water at 310, Indian attacks, 1875 Silver Panic 1873-75, Long depression, Unemployment 14% 1880 Water pipeline, mills on river stop, grades decreasing 1885 Small leasees 1890 Horace Tabor, mine sold for taxes 1895 1900 1905 1910 Faulted extension found 1915 1920 Re-working tailings, Robbing pillars 1925 1930 Open pit, New Technology, New shaft, Sulfides 1935 1940 1945 1950
MINE TIMELINE compared to cartoon geology We can understand the ebb and flow of history from geology
THE VULTURE MINE – LASTING AFFECTS Town of Wickenburg Early description of Wickenburg: The Vulture mine and mill were going full blast. The company paid off every other Tuesday. Money was plentiful, wages high and all seemed to be good spenders. The town had five saloons and one restaurant.
THE VULTURE MINE – LASTING AFFECTS Henry Wickenburg used monies from sale of 300’ of Vulture vein to invest i n Jack Swilling’s scheme to restore the old Hohokam canals along the Salt River. We now call that the Salt River Project and the town is Phoenix.
THE VULTURE MINE – LASTING AFFECTS Grand Avenue cuts diagonally across the Phoenix grid because it was there first – to connect Phoenix farmers to their cash market at Wickenburg and the Vulture mine.
Recommend
More recommend
