Up to the present time there has been very little mining for precious or semi-precious stones in the United States, and then only at irregular periods.  It has been carried on during the past few years at Paris, Maine; near Los Cerrillos, New Mexico; in Alexander County, North Carolina, from 1881 until 1888; and on the Missouri River near Helena, Montana, since the beginning of 1890.  True beryls and garnets have been frequently found as a by-product in the mining of mica, especially in Virginia and North Carolina.  Some gems, such as the chlorastrolite, thomsonite, and agates of Lake Superior, are gathered on beaches, where they have fallen from rock which has gradually disintegrated by weathering and wave action.

Diamond.—­A very limited number of diamonds have been found in the United States.  They are met with in well-defined districts of California, North Carolina, Georgia, and recently in Wisconsin, but up to the present time the discoveries have been rare and purely accidental.

Sapphire.—­Of the corundum gems (sapphire, ruby, and other colored varieties), no sapphires of fine blue color and no rubies of fine red color have been found.  The only locality which has been at all prolific is the placer ground between Ruby and Eldorado bars, on the Missouri River, sixteen miles east of Helena, Montana.  Here sapphires are found in glacial auriferous gravels while sluicing for gold, and until now have been considered only a by-product.  Up to the present time they have never been systematically mined.  In 1889 one company took the option on four thousand acres of the river banks, and several smaller companies have since been formed with a view of mining for these gems alone or in connection with gold.  The colors of the gems obtained, although beautiful and interesting, are not the standard blue or red shades generally demanded by the public.

At Corundum Hill, Macon County, North Carolina, about one hundred gems have been found during the last twenty years, some of good blue color and some of good red color, but none exceeding $100 in value, and none within the past ten years.

Beryl Gems.—­Of the beryl gems (emerald, aquamarine, and yellow beryl) the emerald has been mined to some extent at Stony Point in Alexander County, North Carolina, and has also been obtained at two other places in the county.  Nearly everything found has come from the Emerald and Hiddenite mines, where during the past decade emeralds have been mined and cut into gems to the value of $1,000, and also sold as mineralogical specimens to the value of $3,000; lithia emerald, or hiddenite, to be cut into gems, $8,500, and for mineralogical specimens, $1,500; rutile, cut and sold as gems, $150, and as specimens, $50; and beryl, cut and sold as gems, $50.

At an altitude of 14,000 feet, on Mount Antero, Colorado, during the last three years, material has been found which has afforded $1,000 worth of cut beryls.  At Stoneham, Maine, about $1,500 worth of fine aquamarine has been found, which was cut into gems.