When much smaller and still rounded, they are called _gold dust_, and when flattened, _scales_ or _spangles_. In nature, and when seen in veins of quartz, gold often occurs _foliated_, or in leafy expansions of extreme thinness, or in branchy (_dendritic_) forms, probably made up of minute crystals. It is in the form of very minute grains that the metal is generally disseminated through rocks and auriferous ores of various metals, and these are reduced according to circumstances in methods that will be alluded to in a future chapter. In pepitas and small grains it is carried down by streams and deposited in their beds, the pepitas being usually most abundant where there is reason to suppose considerable disintegration of the surface, and where the action of denuding causes to a great extent is evident. The coast of Africa and the rivers of Europe are examples of the former case, while the Siberian deposits and those of California would appear to belong to the latter.
The following are examples of the constituent parts of various specimens of gold obtained from different gold districts, and will form a useful guide for comparison.
_Table showing the Composition of Native Gold.[19]_
------------------------------------------+-------+-------+-------+------ Locality. | Gold. |Silver.|Copper.| Iron. ------------------------------------------+-------+-------+-------+------ Auriferous sand of Schabrowski, near | | | | Katherinenburg, Siberia (G. Rose) | 98·76 | 0·16 | 0·35 | 0·06 Boruschka, near Nijny-Tagilsk, Siberia | | | | (Rose) | 94·41 | 5·23 | 0·39 | 0·04 Brazil (Darcet) | 94·00 | 6·85 | | Beresovsk, Siberia (Rose) | 93·78 | 5·94 | 0·08 | Sand near Miask, Siberia (Rose) | 92·47 | 7·27 | 0·06 | 0·08 Bogota (Boussingault) | 92·00 | 8·00 | | Washings near Miask, Siberia (Rose) | 89·35 | 10·65 | | Gold of Senegal (Darcet) | 86·97 | 10·53 | | Auriferous sand, Nijny-Tagilsk, Siberia | | | | (Rose) | 83·85 | 16·15 | | Trinidad gold, (Boussingault) | 82·40 | 17·60 | | Transylvanian gold (Ditto) | 64·52 | 35·48 | | Mine of Sinarowski in the Altai (Rose) | 60·08 | 38·38 | 0·33 | ------------------------------------------+-------+-------+-------+------
The gold from California, according to the assay of Mr. Warwick of New York, yields 89·58 per cent, pure gold, and is therefore, about equal to that obtained from the washings of Miask (the richest district in Western Siberia, and that producing the largest pepitas,) and superior, as the assayer remarks, to the gold dust from Senegal.