New data on the geology and characteristics of erionite in New Zealand

Erionite is a naturally occurring zeolite originating from hydrothermal alteration or diagenesis of volcanic rocks. Typically, the two main types of rock in which erionite occurs are basalt and tuff. Erionite generally displays a fibrous morphology, and as with asbestos fibre exposure, respirable fibrous erionite has been linked to cases of malignant mesothelioma. Notably, fibrous erionite appears to be comparable or even more carcinogenic than the six regulated asbestos minerals. The first health issues regarding erionite exposure were observed in Cappadocia (Turkey), and more recently, occupational exposure issues have emerged in the USA. The International Agency for Research on Cancer (IARC) has classified erionite as a Group 1 carcinogen. Nevertheless, undisturbed erionite fibres are not thought to pose a risk to human health. In New Zealand, erionite has been found in surface rock exposures at numerous locations throughout both the North and South Islands, including (from north to south) Kaipara, Auckland, Taupo Volcanic Zone, Banks Peninsula, and the Moeraki coast. Due to the carcinogenic nature of erionite, understanding the distribution and character of the mineral fibres in New Zealand is pivotal. This investigation into erionite in New Zealand is being undertaken using optical and electron microscopy, X-ray powder diffraction and Raman spectroscopy to identify erionite and other zeolites occurring alongside the mineral. Notable examples identified so far include woolly erionite in vesicles within rhyolitic rock in the Canterbury region of the South Island, and asbestiform erionite in the Waitakere Group Volcanics in the Auckland region, of the North Island. Further research is currently ongoing to further delineate the geological occurrence and characterise the mineralogy and chemistry of all erionite samples from New Zealand in an attempt to outline the crystal chemistry of erionite from New Zealand and the related environmental risk hazards.