Note 5 — Chapter XIX · A VISIT TO A GOLD-MINE.
Reading edition
The plasts vary from 3 inches to 15 feet, and their composition varies considerably. Blue clay, coarse sand, quartz, clay-slate, limestone, granite, and syenite occur frequently, as well as iron in the most various combinations; and, more rarely, ferruginous red clay. This last is very tough, and in the rainy season causes the workmen no little difficulty. In return, however, it contains a good deal of gold. In the district of the Olekma the gold deposit rests on a bed of firm rock.