Ferrierite from Tapu, Coromandel Peninsula, New Zealand, and a Crystal Chemical Study of Known Occurrences

T. Sameshima
Geology Department, University of Auckland, Auckland, New Zealand

Abstract: Ferrierite has been found at Tapu, Coromandel Peninsula, New Zealand, as a mineral vein with calcite in altered hornblende andesite lava of the Miocene Beeson's Island Volcanics. The ferrierite is low in SiO2 (63.67%) and high in Al2O3 (13.75%), MgO (3.48%), and BaO(2.35%). The large a axis and cell volume (a 19.236(4), b 14.162(6), c 7.527(3) Å, V 2050 Å3) are consistent with the low SiO2, high Al2O3, high MgO chemistry. Optical orientation and optical sign (a = Z, b = X, c = Y, 2V(-)55°) of the mineral are different from those of the Lake Kamloops ferrierite reported by Graham (1918). Refractive indices α 1.487, γ 1.489, and density 2.136 were measured. Cleavage observed on (100) is perfect and on (001) is imperfect. Using data from eighteen occurrences so far reported including the Tapu mineral, the crystal chemistry of ferrierite has been studied.

Keywords: ferrierite • crystal chemistry • Tapu • New Zealand

Mineralogical Magazine; March 1986 v. 50; no. 355; p. 63-68; DOI: 10.1180/minmag.1986.050.355.09
© 1986, The Mineralogical Society
Mineralogical Society (www.minersoc.org)