Death Valley is not a true valley, which by definition is formed by erosional down cutting. Rather, Death Valley is a structural basin which was formed in the Tertiary due to normal faulting. During normal faulting the rock units of the basin floor were thrust downward and the surrounding mountains were pushed further upward. Active faults persist in Death Valley today and evidence of recent activity includes fault scarps on modern alluvial fans. During the Pleistocene, Death Valley was filled successively by lakes, commonly referred to as Lake Manly. The prolonged wet phases, termed pluvials, were caused by climate change and increased moisture due to glacial melt. Lake Manly filled to significant volumes approximately 10.5 ka, 22 ka and 52 ka. The lake was as long as 145 km and 178 m deep. Insizing by Lake Manly's paleo shores can be still be seen in Southern Death Valley near Mormon Point.
Because Death Valley has the lowest basin in a series of valleys, it continues to serve as the terminal drainage point for the Owens, Mojave and Armagosa Rivers. All water entering the valley as run-off or precipitation evaporates. Consequently salts, including borax, which are in solution due to hydrolysis and dissolution precipitate out. The tremendous deposits of borax in Death Valley today are a result of accumulation of precipitates since the Tertiary, including the significant amount deposited after the evaporation of the Pleistocene lakes.
In the middle of the 1800's borax had been found in various locations in Nevada and California. It was not until 1881 that borax was found in Death Valley. As the story goes, a migrating miner told a man by the name of Aaron Winters (he lived just east of Death Valley) that borax was being mined to the north, and there was a lot of money to be made if someone was lucky enough to find more. Aaron casually asked how one could identify the borax and was informed that a green flame would burn if the borax was treated with alcohol and sulfuric acid and then set alight. Soon after the miner and he parted company, Aaron and his wife, Rosie, went into the desert, collected what he thought was "cottonball" (a type of borax) and performed the experiment. When it worked, Aaron supposedly shouted, "She burns green! Rosie, by God, we're rich."
Aaron sent some borax to William T. Coleman's representative in San Francisco. (Coleman owned a commission house that sold, among other things, borax. He later started mining operations in Death Valley himself.) The representative was a little unhappy when he found out that the borax was miles from anywhere, but he paid Aaron a $20,000 finders fee once he saw the site. But,Aaron had a trick up his sleeve -- he had purchased the water rights to the area. This meant that Coleman could not use the water and had to give Aaron another $2,500 to secure those rights as well.
Coleman, however, was not the only one to stake a claim in Death Valley. Isadore Daunet, a Frenchman who had crossed Death Valley before, came back and quickly set up Eagle Borax Works in 1882. By 1884, he was bankrupt due to the hefty expenses of running the borax refinery and his marriage had failed, and in despair he committed suicide. Coleman acquired the land that Eagle Borax Works was on and he let it fall to ruins. He started his own company, Harmony Borax Works in late 1883. By 1888, Coleman too was bankrupt.
By the 1890's, most marsh or playa deposits of borax were exhausted. Most mining had moved down to Mojave (which is still where the United States get most of its borax today). But in 1907, some mining returned for a short time to Death Valley, because the source rock of the borax was found in the mountains.
One reason that borax has not been mined as readily as other minerals such as gold, is because of the often remote and harsh locations in which it is found. Death Valley was no exception. There were no railroads near by, so the borax had to be hauled by a twenty mule team over 165 miles of treacherous land to Mojave. This was done by specially training the mules .
The mules had different responsibilities and were chosen accordingly. The first two mules, the leaders, were selected for their intelligence and ability to lead others. The next ten were the swing team, and they needed no special training beyond being able to respond promptly to commands such as stop and pull. Then came the eights, the sixes and the pointers. These pairs were specifically trained to leap over the chain when the rig traveled around curves. Finally the last pair were called the wheelers. They needed to be the largest and strongest members of the team and sometimes were draft horses instead of mules. The driver rode the nigh wheeler on downhill stretches in order to operate the brake, which sometimes would give way and the wagons would chase the frantic mules down the hill!
Curves were exceedingly tricky. A mistake could spell death for all. As the team started around a curve, the 120-foot chain tended to be pulled into a straight line between the lead mules and the wagon. The eights, the sixes and the pointers had to jump over the chain at this point so that it would go around the curve and not pull the entire team straight over the edge. These mules would then step sideways until the corner had been turned. This process was an amazing demonstration of training and teamwork.
What do taxidermy, corrugated cardboard, mattresses, eye wash, diodes and the space shuttle all have in common? They all use some form of the element boron in their production.
Although primarily used for centuries in ceramics and as a flux in precious metal works, borax had, at the time the Twenty-Mule teams were laboring to bring it out of Death Valley, become a common staple in most households. It was used for such things as keeping milk sweet, as a water softener, as an aid to digestion, for one's complexion, on dance floors and for removing dandruff. Borates were also said to be excellent for washing carriages and useful in curing epilepsy and bunions.
At the present time borates are used in many and varied ways that affect nearly everyone. The diversity of uses is the result of the multiple properties of borates which include buffering, neutron absorption, esther formation and enzyme stabilization.
Perhaps best known for its use in detergents and soaps, sodium perborate (obtained by reacting borax with sodium hydroxide and hydrogen peroxide) is a gentler bleaching agent than chlorine. Boric oxide (anhydrous boric acid) controls the coefficient of expansion in glass and thus is useful in keeping vacuum flasks, laboratory containers and oven-to-table cookware from breaking when exposed to extreme and rapidly changing temperatures. Small quantities of borates improve the resistance of crystal to dishwashing detergents. In nonsoluble form, borates are added to glazes and enamel coatings to increase their durability and prevent cracking by matching the coefficient of expansion of the glaze to that of the substrate. Borate-containing glazes and enamels are applied to ceramics and metals used in bone china, porcelain fixtures, on refrigerators and stoves, and on the protective tiles that prevent the Space Shuttle from overheating during re-entry into the earth's atmosphere.
Boron compounds are additionally used in fertilizers to aid in plant growth and yield; it acts as a weed killers in concentrated form, in building the lightweight, high-strength structural sections in aircraft, as flame retardants for building materials, plastics and mattresses, as a treatment to the silicon used in electronics parts, and in anti-freeze, brake fluid, face creams and hair products. From colemanite come the resilient fibers used in tires and boats. Further applications are continually being developed.Geologic Setting
Borax is a complex borate mineral found in the playa lakes and other evaporite deposits of Death Valley. The structure of borax contains chains of interlocking BO2(OH) triangles and BO3(OH) tetrahedrons bonded to chains of sodium and water octahedrons. Other borate minerals found in the Death Valley region include: colemanite (calcium borate), kernite (sodium borate), ulexite (sodium calcium borate), pricetite (calcium borate) and proberitite ( sodium calcium borate). These minerals exist in a saturated solution series, which is dependent on the amount of water in the system, as well as the sodium to calcium ratio.
Borate minerals are mined primarily for their content of boron. Minerals containing boron are rare in the earth's crust; they actually constitute less than 3 parts per million in total volume. Deposits mined in California constitute about fifty percent of the world's supply of boron. Other deposits exist in Turkey, South America, China and Russia.
Borax, which is the most common of the Death Valley evaporite minerals, has been used in everything from pottery to medicine since the middle ages. Field specimens of borax are a chalky white due to a reaction that takes place during dehydration. Much of the borax that is found has been altered to tincalconite, a pseudomorph, because of exposure to the air that consequently causes dehydration.
The graph shown above is a plot of the mineral collected at Eagle Spring in Death Valley in March, 1997. It was thought to be a boron mineral when collected. A study of the mineral was undertaken by using both X-Ray Diffraction and Scanning Electron Microscope Kevix 2000 procedures. The procedures were both conclusive in their findings that the collected sample was Gypsum (CaSO4-2H2O)Geologic Setting