gossan

A few years since quite a fever of speculation raged in regard to copper mines, and in the pursuit of the mineral gossan, which is supposed to indicate the locality of veins of ores.

The Resources of North Carolina: Its Natural Wealth, Condition, and Advantages, as Existing in 1869. Presented to the Capitalists and People of the Central and Northern States 1869

What is left is either iron oxide, "gossan," or the oxides of the other metals.

Getting Gold: a practical treatise for prospectors, miners and students

In others, again, are found considerable quantities of soft powdery iron oxide or "gossan," and compounds such as limonite, aluminous clay, etc., which, under the action of the crushing mill become finely divided and float off in water as "slimes," carrying with them atoms of gold, often microscopically small.

Getting Gold: a practical treatise for prospectors, miners and students

Australia reef gold is almost invariably associated with iron, either as oxide, as "gossan;" or ferruginous calcite, "limonite;" or granular silica, conglomerated by iron, the "ironstone" which forms the capping or outcrop of many of our reefs, and which is often rich in gold.

Getting Gold: a practical treatise for prospectors, miners and students

Under weathering conditions pyrite oxidizes, the sulphur forming sulphuric acid, -- an important agent in the secondary enrichment of copper and other sulphides, -- and the iron forming the minerals hematite and limonite in the shape of a "gossan" or "iron-cap."

The Economic Aspect of Geology 1915

Wilkinson found that when the solution of gold chloride was as strong as, say, four grains to the ounce of water, that the pyrites or other base began to decompose, and the iron sulphide changed to yellow oxide, the "gossan" of our lodes, and that though the gold was deposited, this occurred in an irregular way, and it was coated with a dark brown powdery film something like the "black gold," often found in drifts containing much ferruginous matter.

Getting Gold: a practical treatise for prospectors, miners and students

I have tried a further adaptation of this process when treating ores containing a large percentage of iron oxide, where the bulk of the gold is impalpably fine, and contained in the "gossan."

Getting Gold: a practical treatise for prospectors, miners and students

The gossan does not often carry much value, though it may show traces of minerals which suggest what may be found below.

The Economic Aspect of Geology 1915

The gossan is likely to resist erosion and to be conspicuous at the surface, -- though this depends largely on the relative resistance of the wall rocks, and on whether the gangue is a hard material like quartz, or some material which weathers more rapidly like limestone or igneous rock.

The Economic Aspect of Geology 1915

In the extreme eastern portion of Ashe county the gossan ores (brown hematite) of the Ore Knob copper lode, bear mention.

North Carolina and its Resources. North Carolina. Board of Agriculture. 1896