When I started for the mine, accompanied by detectives and guards, we all carried pistols in holsters strapped under our arms. En route, we spent Christmas amid the smell of sagebrush and the glorious sunset lights of a purple desert. Once more I murmured, “So this is natural history.”
I was employed to examine the Quartette Gold Mine, and the geologic mystery of the origin of a million dollars in dirt between a level 200 feet down and another at a depth of 500 feet. The million dollars was along a crushed, slipped, so-called vein, where a fault followed the upright bedding of just such gneisses, granite dikes, and schists as had made Crooks Complex in the Bradshaws. Where gold was richest, minerals were richest—beautiful orange-colored wulfenite, green chrysocolla, blue azurite, onyx, quartz, and calcite. Everywhere were quantities of gouge, or crushed clays, from grinding walls. Native gold particles were distributed through all this.
The schists were filled with lava fissure fillings, and the mine was where this pattern of bands was interrupted by a very ancient greenstone or basalt body. Hot fluids of the volcanic period, deep underground, had accompanied fault slipping or fracture where the ore was, the vertical fault parallel to the upright layers and across the greenstone contact.
Ore and gold particles were directly related to fracture, to the fault slipping on an upright crack of one mountain block against another, to the hot vapors depositing the mineral collection, and to renewed crushing and sliding on the mountain blocks. This was during or following some part of the volcanic period when all the cracks were injected with andesite lavas, or what the miners call porphyry. The origin of the minerals was in lead and copper sulfides which lie deeper down.
A hundred miles to the northeast is the Grand Canyon, and all around are granite mountains, just as in Arizona. These Searchlight schists are the same Algonkian ancient strata, recrystallized and granitized, that make the inner gorge of the canyon, and are traversed up cracks by volcano-making lavas, such as dot the north bank of the canyon with crater cones. Above in the canyon are the horizontal strata from Cambrian up to the Coal Measures and beyond. The vast maze of castles and turrets is a net of branch valleys of the Colorado, trenching through these old seabed deposits.
Including Searchlight ore, the whole history going backward is top country desert, deep trench, strata piled in rivers and sea bottoms for 500 million years, and lastly faulting and cracking that squirted steam and made gold minerals over and over again during the last 100 million years. There were at least a dozen revolutions that lifted and lowered mountain ranges and continents for 2,000 million years, and the remains of iron-eating bacteria and of seaweeds and other living things that go back for 1,500 million years. Through it all are granite injections as a process, as a mystery, going over the whole range of years in different ages, and meaning what?
One of the puzzles of Grand Canyon, Bradshaw Mountains, and Searchlight—if not also of New England, the Black Hills, and the Yellowstone—is faulting. A fault is what a geologist means by a crack down deep where the country rock has dropped down on one side so as to make a discordance across country. Earthquake faults make a visible bank or step or sidewise slip, changing the surface after an earthquake.
The northwestern states are partly mapped as fault block mountains. The island of Hawaii has a series of fault step blocks southeast, slipping toward the ocean. The steep east face of the Sierra Nevada is a fault fracture.
Professor Shaler once stopped me on the street and said of my field work, “Jaggar, you don’t teach faulting enough.” Faults were shown along straight lines on the color maps of formation in the old Boston books, and were located by guesswork if glacier deposits covered up the ledges. It seemed to me that faults ought to be proved or else omitted from the maps. Probably I too was wrong, for faults or cracks completely concealed by soil and strata are tremendous unknown lines on the globe.
The Searchlight ore body is certainly a fault fracture, and so are those of Tonopah and hundreds of mines. It was digging that proved it. The cracking and slipping and steaming and mud-making on the fissure are what brought up the minerals.