California Beaches and Precious Gem Stones and Pebbles

The California beaches have furnished some of the most interesting ornamental pebbles, the greater number being of chalcedony or agate weathered from an amygdaloidal rock, while a few are of jasper or fossil coral. Their variegated color-markings made them very attractive ornamental objects in themselves, and there is reason to believe that centuries ago the Indians of this region valued them as talismans or amulets. At present the finest specimens are gathered from Pescadero Beach in San Mateo County, about twenty-four miles west of San Jose, Redondo Beach, fifteen miles south of Los Angeles, and also from Crescent City Beach, in the northern part of California. On Moonstone Beach, Santa Catalina Island, many beautiful quartz and chalcedony nodules have been picked up, which have weathered out of ryolite rock of sanidine feldspar and quartz. It has been quite a custom for guests of the hotels to go down to Redondo Beach and gather these pebbles, and some of those collected by enterprising natives are placed in a bottle of water to bring out the beauty of their colors. Sometimes they are drilled and strung on flexible wire to form long chains or necklaces. Several pebbles presumably from Redondo Beach were found, in 1901, in an Indian grave, where they were probably placed as amulets for the dead.

The occurrence of fluid cavities in quartz, chalcedony, sapphire, and other minerals, is due at times to cavernous structures formed during the growth of these minerals, when the crystalline substances, for some reason, instead of filling these up solid, will avoid the caverns and enclose the liquid of crystallization. In agate inclusions this is found with silicious content, possibly due to the fact that it is to an extent carbonic acid gas, or water containing salt or some other foreign substance. In agate chalcedony, whether in pebbles as minute as a pinhead, or in amygdules several feet across, the liquid is enclosed because the walls of the gaspores in the rock, which are frequently almond-shaped, are gradually becoming smaller, or rather the walls thicken by the deposition of the silica forming agate, chalcedony, or any impenetrable layers, or else an impenetrable form of quartz; then again, frequently toward the centre or when the liquid forms less rapidly, or through some change, the quartz becomes crystalline, either colorless, smoky, or amethystine, and this is due to various inclusions. This gradual thickening of the walls means that the aperture into which the liquid penetrates becomes smaller and smaller until at last it is entirely sealed, so that it becomes enclosed in a kind of nature's water-bottle, these being sometimes as large as in the chalcedony specimens from Uruguay; this is also the case with the hydrolites and the enhydros, when they can be shaken and the water rattles as in a bottle.