What is golds luster

Soluble only in aqua regia. In Group. Native Elements. Striking Features. Golden-yellow color, extreme heaviness, lack of tarnish, and malleability and ductility. In Quartz vein s and high temperature hydrothermal deposit s, as well as placer deposit s. Rock Type. Sedimentary , Metamorphic. Popularity Prevalence Demand Native Gold. Picture Rock - Mixture of Gold vein s within a Quartz matrix. Gold has been used as a precious metal throughout the history of mankind. This is due to its resistance , beauty, rareness, and the fact that it is very easy to work with.

Many exotic gold ornaments from the past have been found. Especially noteworthy are the golden ornaments from the tombs of the Pharaohs in Egypt, where gold masks, statues, coins, and much jewelry was archeologically excavated.

Gold has been used for coinage throughout the centuries, and is currently accepted internationally as a standard value. Nowadays, the main use of gold is for jewelry. As pure gold is easily bent and dented, it is always alloyed with other metals when used in jewelry. This makes it more durable and practical for ornamental use. The purity of the gold based on the alloyed metal is measured in karat weight.

The karat measurement determines the percentage of gold to other metals on a scale of 1 to 24 , with 24 karats being pure gold. Due to gold's distinctive properties as a metal, it has several industrial uses. It is used in photography, dentistry, coloring, and is currently being studied for cancer treatments.

Much of the Gold mined is from large mining operations where the Gold is smelt ered for commercial use, and although many commercial gold mines exist, mineral specimens and crystals are hard to come across. China and South Africa have been the worlds two largest Gold producers, but collectors will rarely if ever see a Gold specimen from these countries due to the restrictive nature of the mining operations.

This locality list will restrict itself to specific occurrences where noteworthy specimens extracted have made their way to collections. Australia, a large gold producer, has the famous occurrences of Kalgoorlie, Western Australia; and the Bendigo area, Victoria. In the U. California, home to the Gold rush in the Sierra Nevada Mountains, abounds in historical mining towns and many scattered occurrences.

In metals, when very large numbers of atoms are brought close to each other, the low and high energy bands can overlap, forming a nearly continuous band of available energy levels, where electrons may move freely. The color of metals can be explained by band theory, which assumes that overlapping energy levels form bands.

The mobility of electrons exposed to an electric field depends on the width of the energy bands, and their proximity to other electrons. In metallic substances, empty bands can overlap with bands containing electrons. The electrons of a particular atom are able to move to what would normally be a higher-level state, with little or no additional energy. The outer electrons are said to be "free," and ready to move in the presence of an electric field.

Some substances do not experience band overlap, no matter how many atoms are in close proximity. For these substances, a large gap remains between the highest band containing electrons the valence band and the next band, which is empty the conduction band.

As a result, valence electrons are bound to a particular atom and cannot become mobile without a significant amount of energy being made available. These substances are electrical insulators. Semiconductors are similar, except that the gap is smaller, falling between these two extremes.

The highest energy level occupied by electrons is called the Fermi energy, Fermi level, or Fermi surface. Above the Fermi level, energy levels are empty empty at absolute zero , and can accept excited electrons. The surface of a metal can absorb all wavelengths of incident light, and excited electrons jump to a higher unoccupied energy level.

This creates current, which rapidly discharges to emit a photon of light of the same wavelength. So, most of the incident light is immediately re-emitted at the surface, creating the metallic luster we see in gold, silver, copper, and other metals.

This is why most metals are white or silver, and a smooth surface will be highly reflective, since it does not allow light to penetrate deeply. If the efficiency of absorption and re-emission is approximately equal at all optical energies, then all the different colors in white light will be reflected equally well. This leads to the silver color of polished iron and silver surfaces.

The efficiency of this emission process depends on selection rules. However, even when the energy supplied is sufficient, and an energy level transition is permitted by the selection rules, this transition may not yield appreciable absorption.

This can happen because the energy level accommodates a small number of electrons. For most metals, a single continuous band extends through to high energies. Inside this band, each energy level accommodates only so many electrons we call this the density of states. The available electrons fill the band structure to the level of the Fermi surface and the density of states varies as energy increases the shape is based on which energy levels broaden to form the various parts of the band.

If the efficiency decreases with increasing energy, as is the case for gold and copper, the reduced reflectivity at the blue end of the spectrum produces yellow and reddish colors. Metals are colored because the absorption and re-emission of light are dependent on wavelength. Gold and copper have low reflectivity at short wavelengths, and yellow and red are preferentially reflected, as the color here suggests.

Silver has good reflectivity that does not vary with wavelength, and therefore appears very close to white. Silver, gold and copper have similar electron configurations, but we perceive them as having quite distinct colors. Electrons absorb energy from incident light, and are excited from lower energy levels to higher, vacant energy levels. The excited electrons can then return to the lower energies and emit the difference of energy as a photon.

If an energy level like the 3d band holds many more electrons than other energy levels then the excitation of electrons from this highly occupied level to above the Fermi level will become quite important. Gold fulfills all the requirements for an intense absorption of light with energy of 2.

The color we see is yellow, as the corresponding wavelengths are re-emitted. Copper has a strong absorption at a slightly lower energy, with orange being most strongly absorbed and re-emitted. In silver, the absorption peak lies in the ultraviolet region, at about 4 eV.

Significant quantities are also present in the U. Gold is found in two major types of deposits. Lode deposits are where gold is found in veins in rock.

The second type is called a placer deposit that is formed by moving water that has eroded gold out of lode deposits. When the speed of the water in a river slows sufficiently, the heavy gold falls to the bottom and accumulates in the sand of the riverbed.

Another source of gold is as a by-product of copper and silver mining. Gold is so valuable that it is worth the effort to recover even minute amounts from copper and silver ore. It is estimated that the total amount of gold yet to be removed from the Earth is , tons.

Approximately one-fifth of the total resources of gold in the world are by-products from copper and silver ore processing. In the United States, Nevada produces the majority of the gold followed by Alaska.