Gold particles that are rough and hackly or have adhering quartz prove that the gold has not been much worn and indicates that the gold is close to its original source. Gold that is pounded and worn into smooth flat nuggets or flakes has travelled some considerable distance from its source. These characteristics apply regardless of the size of the individual pieces, although the finer sizes naturally travel farther, and fine flaky pieces will travel farther than rounded or shot-like pieces of equal weight.
An almost constant characteristic of placer gold from any one creek is its fineness, example the gold-silver ratio. In British Columbia ,placer gold ranges in fineness from about 700 parts per 1,000 for gold from Cherry and Monashee Creeks to about 970 parts for gold from Goat River. Most placer gold ranges from 800 to 900 fine. The numerical average of the average fineness of gold from 173 streams is 861.
Placer gold is an alloy, mainly of gold and silver, but may contain small amounts of platinum, copper, iron, and other elements. Its colour depends largely on the amount of silver present, and also on the presence or absence of surface films of iron oxide. The colour, size, and general shape of the gold pieces present so characteristic an appearance that experienced gold-buyers can tell from which creek any packet of gold came from.
Placer gold occurs in sizes ranging from large nuggets to minute particles requiring many thousands to yield anything of value. Coarse gold will not pass through a IO-mesh screen, and fine gold will be retained on a 40-mesh screen. Flour gold includes all sizes that will pass through a 40-mesh screen. The Cariboo was remarkable for its coarse gold, whereas mostly fine and flour gold was recovered from the bars and benches of the Fraser River below Hope, and from the Peace River.
Nuggets are formed from plates and masses of gold which have been released from lode deposits by weathering, and pounded and rolled into solid lumps. The recovery of large pieces of gold from lode-mining at the Cariboo and Bridge River areas demonstrates that gold-bearing veins contain gold of sufficient size to form large nuggets. There is no evidence to show that chemical deposition of gold in the gravel has played any part in the formation of placer-gold nuggets.