One of the most historic in the August birthstones, sardonyx is a combination of two kinds of chalcedony (cryptocrystalline quartz): sard and onyx. Bands of brownish pink to brown to darkish orange sard alternate with ordinarily white or black layers of onyx. Of course, this month is Valentine's Day, and https://www.gemsbiz.com/blog/explore/birthstones-by-zodiac-sign