New Zealand Kauri Amber — Sub-fossil Resin from the Agathis australis
New Zealand Kauri Amber — Sub-fossil Resin from the Agathis australis
Geologically young copal from the North Island gum-fields, traded historically as kauri gum and occasionally as amber
New Zealand kauri amber is a sub-fossil tree resin from the kauri tree (Agathis australis), the great softwood conifer of the North Island of New Zealand. The material is geologically young — typically a few thousand to a few tens of thousands of years old, occasionally older but rarely approaching the millions of years that characterise true amber from Baltic, Dominican, or Burmese deposits. By the strict scientific definition the material is therefore copal rather than amber, but the trade name kauri amber is in widespread use, the material has been commercially significant in New Zealand since the nineteenth century under the simpler name kauri gum, and the broader public usage treats the material under both names. The New Zealand-specific term for the older material is also retro: gum-diggers and the historical gum trade are part of the country's settler-colonial history, and a substantial documentary record survives in New Zealand museum collections and the historical literature.
The kauri tree and the resin
Agathis australis is one of the great trees of the Southern Hemisphere — a long-lived, slow-growing softwood that historically dominated the lowland forests of the northern North Island, with individual trees reaching heights of fifty metres and trunk diameters of over four metres, and ages of two thousand years and more. The species produces a thick, sticky resin that hardens on exposure to air and falls to the forest floor as the bark sheds. Over centuries the resin accumulates in deposits within the soil and the underlying clay, sometimes reaching depths of metres in the swampy areas where preservation conditions are most favourable.
The kauri forests of the North Island were extensively logged in the nineteenth and early twentieth centuries for their valuable timber, and the cleared land — much of it converted to pasture — became the principal source of the gum-digging industry that worked the resin deposits left behind by the cleared trees. The peak of the gum trade was the 1890s and early 1900s, with annual exports running into thousands of tonnes and a significant economic contribution to the colonial economy.
The historical commercial use
The principal nineteenth and early twentieth-century use of kauri gum was industrial: the resin was the principal raw material for high-quality varnish manufacture, and the linoleum and floor-covering industries also consumed substantial quantities. Kauri gum varnish was prized for its hardness, its rapid drying, and its compatibility with traditional pigments and binders, and the material was a globally significant export commodity from New Zealand into the British, American, and European varnish markets.
The introduction of synthetic resins in the 1930s and the subsequent development of modern alkyd, urethane, and acrylic varnish systems progressively displaced kauri gum from the industrial market. By the 1960s the commercial gum trade had effectively ended, and the surviving production has been principally for the jewellery, decorative, and collector markets.
Properties and identification
Kauri gum has a refractive index of approximately 1.54, a specific gravity of 1.05 to 1.07, and a Mohs hardness of approximately 2.5 — softer than Baltic amber and substantially softer than the harder Dominican and Burmese amber. The colour ranges from pale yellow through golden yellow to deep brown, with occasional greenish, reddish, and almost black material. Surfaces are typically smooth and glassy in fresh material, with patination and oxidation developing over time on exposed surfaces.
The principal identification challenge is the distinction from older true amber. Infrared spectroscopy provides the cleanest distinction — kauri gum, like other copal, retains residual volatile components that produce characteristic absorption bands distinct from the more polymerised true amber. The hot-needle test (kauri gum melts and emits a characteristic resin smell at lower temperatures than true amber) is a traditional but destructive secondary indicator. Solvent solubility is also higher in kauri gum than in true amber, with the material softening or partially dissolving in alcohol, ether, and turpentine.
Inclusions
Kauri gum can contain biological inclusions — insects, plant fragments, occasional vertebrate remains — but the inclusion fauna is necessarily New Zealand-endemic and reflects the recent geological age of the resin. The inclusion record is therefore much narrower than the diversity preserved in older true ambers, but it is of substantial scientific interest as a record of the recent New Zealand forest ecology and palaeoecology.
In the trade
For buyers and dealers, kauri gum or kauri amber should be approached with appropriate disclosure. The material is not Baltic amber, is not Dominican amber, is not Burmese amber, and the trade should not represent it as if it were. The material has its own legitimate market position — as a New Zealand cultural and historical material, as an attractive and accessibly priced jewellery resin, and as a specialist collector category — and that position is best served by honest description.
Carved and turned kauri gum pieces from the early twentieth century are themselves of historical interest and are part of the New Zealand decorative arts heritage. Modern production for the jewellery market continues at small scale, with cabochon and tumbled pieces, beads, and decorative inlays. Prices are accessible by the standards of true amber, and the material has a steady niche audience.