J meaning in Earth Science ?

Jade is a mineral, much used in some cultures as jewellery and for ornaments, mostly known for its green varieties, though it appears naturally in other colors as well, notably yellow and white. Jade can refer to either of two different silicate minerals: nephrite (a silicate of calcium and magnesium in the amphibole group of minerals), or jadeite (a silicate of sodium and aluminium in the pyroxene group of minerals).

Jade is well known for its use in East Asian, South Asian, and Southeast Asian art.

Jade also has an important place in Latin America such as Mexico and Guatemala. The use of jade in Mesoamerica for symbolic and ideological ritual was highly influenced by its rarity and value among pre-Columbian Mesoamerican cultures, such as the Olmec, the Maya, and the various groups in the Valley of Mexico. Although jade artifacts have been created and prized by many Mesoamerican peoples, the Motagua River valley in Guatemala was previously thought to be the sole source of jadeite in the region.