jades

Jade is a term used for two distinct minerals used as gemstones: jadeite and nephrite. Although grouped together in jewelry and art as jade, they have different chemical compositions: jadeite is a sodium aluminum silicate (NaAlSi2O6) and nephrite is a calcium magnesium iron amphibole (a tremolite–actinolite series). Both are typically green but can occur in white, gray, yellow, lavender, or black.

Geology and formation: Jadeite forms under high-pressure, low-temperature conditions in subduction-zone metamorphism of pelitic rocks and ultramafic rocks; nephrite forms by metasomatic replacement of tremolite–actinolite in serpentinite. Major modern sources include jadeite from Myanmar and nephrite mined in Canada (British Columbia), China, Russia, and the United States, with New Zealand pounamu (nephrite) having particular cultural significance for the Māori.

Historical and cultural significance: Jade has long been valued for durability and beauty. In China, jade signifies virtues such as benevolence, wisdom, and courage; imperial jadeite deposits produced some of the finest carvings in East Asia. In the Americas, Mesoamerican cultures valued jade for ritual objects and adornment, and jade artifacts frequently appear in tombs and monuments.

Properties and care: Both jadeite and nephrite are very tough, among the most resistant natural stones; Mohs hardness is typically around 6–7. They display a silky to waxy luster and a glassy to translucent appearance when well cut. They can be carved and polished to a high finish. Cleaning with warm soapy water is usually sufficient; avoid harsh chemicals and severe or sudden temperature changes. Distinguishing jadeite from nephrite generally requires gemological testing or professional analysis.