The gemstone known as 'nephrite' was named after the Greek word for 'kidney', which refers to its believed healing ability to cure kidney diseases. Nephrite jade is recognized as one of the two distinct pure mineral forms classified as jade (the other is jadeite). In fact, nephrite was believed to be one and the same as jadeite up until 1863. Nephrite is a fibrous aggregate variety of tremolite-actinolite, whereas jadeite is a member of the pyroxene mineral family. Nephrite is more common than jadeite and although it is slightly softer than jadeite, it is actually tougher overall due to its denser structure. Almost all traditional Chinese jade typically refers to nephrite since there throughout history; there are no actual jadeite deposits that have been discovered in China. Mutton fat jade is a form of nephrite that is highly sought-after by jade collectors.
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