Gold

Deposits

Mining and Exploration

Geology Handbook

Gold

Gold is a highly sought after mineral, both for its monetary value and its special properties as well as a long history of Gold being a symbol of wealth the world over.

Gold only (there is one exception) is found as a free element. The Gold (Au) element does not form bonds with other elements to form any unique minerals. This is represented by one of its special properties – it will not oxidize/rust or tarnish. This makes it a great choice for jewelry and commerce.

Golds other very useful property is its electrical conductivity which makes it very useful in electronics and computers. Future gold mines maybe todays computer waste.

Gold deposits

Narrow Vein, High Grade Gold

The original source of gold deposits owes its formation to one of the unique properties of the mineral Gold. It does not like bonding with other elements. As a result, it basically forms as free gold wherever super heated, super pressurized liquids force their way into.

These Fluids are rich in silica and other minerals, the silica allows for creation of quartz, and since gold does not like bonding with anything it solidifies all by itself, after the other elements have bonded and created other more complex minerals. A few other more common minerals will form in quartz veins associated with gold including pyrite, pyrrhotite, galena, arsenopyrite, silver as well as other base metallic minerals. These are only indicators of the potential for gold and are referred to as indicator minerals.

Indicator minerals tend to be general, with one or two specific to each gold deposit. The presence of the indicator mineral is only an indication that gold may be present.

Narrow vein Gold requires quartz veins (of course), usually less than a meter wide, indicator minerals will be present and exposed surfaces may form rust stains from the indicator minerals if iron based (the most common).

In the above picture, the known gold deposit the primary indicator minerals are fine grained arsenopyrite and pyrrhotite. In this drill core there is a nicely mineralized quartz vein with both those indicators as well as the common pyrite. This peice of core did have high grade gold speckled in amongst the arsenopyrite.

All three of these indicator minerals are iron based and at surface this quartz vein would have abundant rust staining.