Pounamu is a Mori
collective term for semi-precious stone scientifically referred to as nephrite,
semi-nephrite, jade or bowenite (tangiwai) that is composed predominantly of
metamorphic tremolite in a felted, fibrous texture. It is Aotearoa/New Zealand's
icon mineral material. Ownership and management of this important taonga
(treasure) has been vested in Te Rnanga o Ngi Tahu as part of a Treaty of
Waitangi settlement process. Increasing demand from the tourist, jewellery,
fashion and sculpture industries, as well as cultural renaissance, has placed
pressure on the pounamu resource. This had led to nephrite importation,
allegations that foreign material is being marketed falsely as New
Zealand pounamu, and wider concerns over the
potential for exploitation/over-use and theft of genuine pounamu.

Research is underway to
characterise different pounamu source regions by defining their genetic
fingerprint'. The geological age and radiogenic isotopic composition of
Aotearoa/New Zealand pounamu is distinguished from other nephrite jade
occurrences overseas, due to relatively young cooling ages. Strontium isotope
ratios distinguish pounamu from different source areas within Aotearoa/New
Zealand (whakapapa), with signatures reflecting the host terrane rocks (their
family) and their position in a sequence of metamorphic events (their
generation). The research will provide a tool for archaeological research,
trademark and resource protection.

Mineral resource
assessments normally aim to define the total volume/tonnage present, which is
generally assumed to be finite, applying drilling and geostatistical modelling.
Pounamu resource assessment requires a different approach, as its intrinsic
value is insufficient to warrant modern exploration methods (eg drilling,
geophysics). Pounamu is only known to occur at a restricted few in-situ
(hard-rock) localities. It is primarily found in transported (alluvial) detrital
river and glacial outwash deposits, where collectable material has short term
variability due to erosion and transport processes. A new methodology is being
developed aiming to define:

the total resource present,

the relative rate of change in the availability of that
resource through erosion and other geological processes,

active areas where new material is likely to be exposed (eg
by erosion), and

appropriate extraction rates for sustainable use.
The
methodology will provide a holistic overview of the resource in different
regions of Aotearoa/New Zealand, and may be applicable to other transient or
restricted natural resources that occur within geologically active environments
(eg supplies of driftwood on beaches).