Jasper, an aggregate of microquartz and/or chalcedony and other mineral phases, is an opaque, mpure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron inclusions. The mineral aggregate breaks with a smooth surface and is used for ornamentation or as a gemstone. It can be highly polished and is used for vases, seals, and snuff boxes.
Onyx is a banded variety of the silicate mineral chalcedony. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands: agate has curved bands and onyx has parallel bands. The colors of its bands range from white to almost every color (save some shades, such as purple or blue). Commonly, specimens of onyx contain bands of black and/or white.This necklace has a lobster clasp and is adjustable from 18 inches to 20 inches.