Description
Nephrite forms through a broader set of pathways. Researchers have proposed an evolutionary classification in which nephrite can form by direct precipitation in veins, through the development and evolution of metamorphic fabrics during folding and deformation in shear zones (with dissolution and re-precipitation as the key process mediating fabric change), or by later brecciation and disruption of previously formed nephrite.
The common thread is contact between silica-bearing fluids and magnesium-rich ultramafic rock. This reaction happens at lower pressures than jadeite formation, which is why nephrite can form in mountain belts, fault zones, and metamorphic terrains far from any subduction zone.
