The more facts you have about gold in general, the better off you’re going to be as a prospector, and the greater your ability to locate and recover that precious yellow metal. Knowing something about how gold forms in veins encased in host rock can only enhance what you already know about placer mining and increase your level of understanding.
A distinct linear or lens-like body of crystallized minerals with a host rock (sometimes called “country rock“). One of the most common forms of crystallized veins in gold mining is the mineralized quartz vein. It is this vein material (quartz or other crystallized minerals) that contains precious metals like gold or silver, either in a chemical state (sulfide form) or as physical metal (“free-milling“).
Gold veins can sometimes be many feet thick. Stringers, on the other hand, are very narrow veins that rarely exceed six inches in width, although their lengths are not necessarily similarly affected. Stringers are more commonly seen as vein material three or four inches, sometimes only an inch or two in width. Quartz stringers in host rock are seen quite often, even in non-gold bearing regions.
Quartz And Gold Stringers
When a localized area of heavily mineralized country rock containing vein material breaks the earth’s surface through erosion or geological forces, this is known as a blow out. Most blow are contained within a 10-30 yard radius. The blow-out descriptor tends to refer to the scattering of eroded ore on the ground around the blow out and/or the fact that powerful geological forces such as buckling, pressure, magma flow, etc. forced mineralized material to pop up or blow out above the earth’s surface.
An outcropping is a visible exposure of country rock (including bedrock) projecting above the surrounding earth’s surface. Rocky outcrops in gold-bearing regions can be heavily mineralized and shot through-and-through with vein material they should always get a closer examination out in the field. Outcrops are usually fairly large in scale and in some instances can cover quite a bit of ground.
A shelf-like formation or ridge that is usually found on the crest of hills or along their upper slopes. Some ledges can exhibit stringers, veins, or even significant amounts of sulfides or oxides. Historically, some very rich ledges have been found throughout Canada and the U.S., and a few ledges have become the subject of famous treasure legends.
You wont hear this term used much in North America but it’s commonplace among Aussies and New Zealanders, as well as South African gold miners. In essence, a gold reef is what we call a vein here in Canada and the U.S.
Aside from quartz, other crystallized carriers of gold in veins include calcite, galena, pyrite (or “fool’s gold”), and chalcopyrite. The gold contained in these sorts of carriers can be present as free-milling metal or it can remain in sulfide or chemical form. These latter forms are known as refractory ores and they require specialized treatment to leach, process, and recover the gold within them. You should also note that many gold sulfide veins are identified by the presence of calcite as well as small amounts of silver. Carbonates can also make an appearance in sulfide gold ores and some of the largest hard-rock gold deposits are based on extremely rich carbonaceous ore bodies containing sub-micron particles of the precious yellow metal.