Tangiwai is the most ancient form of pounamu. It is bowenite rock, which is different in composition to the more common nephrite. Most Tangiwai is sourced from two isolated areas at Piopiotahi (Milford Sound), Poison Bay and Anita Bay and deposits found in Nelson. Tangiwai takes its name from the tears that come from great sorrow. Tangi means "to cry" and Wai means "water", or "tears". Koko-Tangiwai, the longer name for this stone, refers to a deep sorrow that is never completely healed. There are many sad stories that tell of Tangiwai pounamu's origins.
