=Gold.= The gold of the Chocó placers has been widely known since the Spanish Conquest. Four hundred million dollars was taken by the Castilians from shallow waters and easily worked river banks. In recent years a number of companies have been operating. The Pato mines cover 40,000 acres near Zaragoza, population 2700, Antioquia, where a dredge is operated. At the Nechi mines the dredging cost is 9 cents a yard, the return about 75 cents. In Antioquia there are 20 rivers with gold alluvium, but operations are chiefly on the Cauca, Nechi, Pato, and Porce. The bench gravel is very deep and can be worked profitably (except at times by the natives) only with machinery, as is the case generally. Therefore considerable capital is necessary for a successful enterprise. More than 12,000 gold bearing sites are known in Antioquia; many in Nariño, Caldas, El Valle, Tolima and Chocó. The gold production in Colombia since the Conquest is estimated as above $600,000,000 and that of silver as $30,000,000. =Emeralds.= The most famous mining industry of the country is emeralds; for nowhere else are they produced in quantity and here are the best. The mines were worked long before the coming of the Spaniards, and the actual labor has been performed by the Indians ever since. The mining has been a Government monopoly. The area is a region of 4000 square miles, but the only mine recently operated is the Muzo, 92 miles northwest of Bogotá. It is now worked by the open system though formerly by tunnel. The workers live on the ground in buildings provided for the men and officers, with police to prevent thieving. Present operations are in almost vertical cliffs rising from 100 to 550 feet above small valleys. The loose soil is not removed by water, as is stated elsewhere; the emeralds are separated from the soil by a dry method; water is used to carry away the detritus and also to wash the residue left by material from rotten veins in order to expose small emerald crystals. The output in normal years approaches 800,000 carats. No attempt should be made to obtain a possible concession without thorough investigation and ample capital. The same may well be said of any mining venture. A concession for emerald mining has been secured by an American company. OTHER INDUSTRIES