By far the most ancient with the August birthstones, sardonyx is a combination of two kinds of chalcedony (cryptocrystalline quartz): sard and onyx. Bands of brownish red to brown to darkish orange sard alternate with commonly white or black layers of onyx. Turquoise gives Cancers the liberty to put them https://www.gemsbiz.com/blog/explore/birthstones-by-zodiac-sign