Few people know that gold actually forms crystals in nature. While the beauty of natural gold is widely appreciated by both prospectors and mineral collectors, the pinnacle of beautiful natural gold specimens are the spectacular crystalline forms. As a result, these specimens of golden scales, plates, ribbons and crystals are normally saved and treasured. Unfortunately, the natural growth conditions that form most gold deposits only rarely create these very attractive specimens.
At most mines, native gold is more normally found in the form of irregular masses and blobs in quartz or sulfide veins, or as impregnations in the country rock adjacent to mineralized fissures. In fact in most modern mines the gold is in the form of very tiny particles, too small to easily see with the unaided eye. In placer gravels, the wear of the erosion process means gold normally is pounded into the outwardly rounded forms of scales, grains, slugs, and nuggets. While large alluvial nuggets are beautiful and valuable in their own right, the crystalline forms are still the ones most highly valued. In fact, the value of crystalline gold in an attractive matrix specimen can exceed the intrinsic metal value of the gold by a factor of 10 to 100 fold in some cases.
Although gold only rarely shows its attractive crystalline forms, where the geologic conditions are favorable, as in cavities or other locations where growth and expansion is not hindered by a lack of space, gold obeys the natural laws of its crystal growth and crystallizes in various isometric (cubic) forms. This partly explains the rarity of fine crystalline gold specimens. This is because open voids are uncommon in and of themselves. Normally, the walls of the cavity limit the lines of crystal growth, or growth is cut off by the concurrent growth of another mineral, such as calcite or quartz. Often any voids that do exist are later filled with quartz or other materials, including clays.
In addition, large single crystal growth requires stable conditions that support slow growth - at least growth slow enough to lead to the formation of a few large crystals rather than millions of tiny ones. Faster growth will support the development microscopic pieces or at least mossy and dendritic forms. Gold crystallizes in the isometric system, and usually forms crude octahedrons, but specimens showing dodecahedrons, cubes and trapezohedrons are also found. Crystals are rarely perfect, and are normally irregular, sometimes exhibiting unusual wiry, reticulated or dendritic shapes. Many forms also show some sort of distortion of the crystal, some with extreme distortion. Crystal twinning is common in gold.
Between the combined effects of all the different crystal forms, twinning and a range of possible crystal distortions, gold can found a very large variety of crystalline forms, all of which have their own attractive appearance. The number of potential combinations is so large that all the possible combinations are hard to fathom. Beautiful wire forms are found in a number of locations, with one of the most famous locations being Farncomb Hill in the Breckenridge District of Colorado (beautiful leaf and other forms are found there as well).
Many of the dendritic forms are also beautiful, and one of the most beautiful dendritic forms of gold are the herring bone style dendrites, with some of the finest examples of this being the "chevron" gold of northern Nevada. California produces some specimens of ribbons and sheet gold, some with attractive crystal patterns on their surface, and these are also highly sought after.
