Li-Bearing Stevensite from Moldova Nouă, Romania

Virgil Ianovici, Gheorghe Neacşu1 and Vasilica Neacşu1
National Council for Environmental Protection, 5 Av. Ilie Pintilie 71902 Bucharest 32, Romania
1 Geological & Geophysical Prospecting Enterprise, 1 Caransebeş Street, 78344 Bucharest 32, Romania.

Abstract: Li-bearing smectite minerals occurring as hydrothermal alteration products of magnesium silicate minerals in skarns associated with the Moldova Nouă Romania, porphyry copper deposit were examined by X-ray powder diffraction, infrared spectroscopy, and thermal and chemical analyses. Li-bearing smectite containing 0.45–0.50 Li/unit cell is common, whereas smectite containing 0.21–0.33 Li/unit cell is less common. Both materials coexist with talc and kerolite. The Li-bearing smectite minerals (b = 9.111 Å) contains semi-ordered or ordered stacking and is highly crystalline, similar to saponite. After 3-yr storage under laboratory conditions in an air-dried state (RH = 50%) or after heating for 2 hr at 100°, 200°, 300°, or 400°C, the Li-bearing smectite minerals showed characteristics of a regular 1:1 interstratification of anhydrous and dihydrate layers. Some segregation of the anhydrous, monohydrate, and dihydrate layers was noted.

The amount of Li-for-Mg substitution was found to be close to that in hectorite, and the number of octahedral vacancies was similar to that in stevensite. This Li-bearing smectite apparently formed directly from colloidal suspensions at atmospheric temperature and pressure.

Key Words: Hectorite • Hydration • Interstratification • Lithium • Smectite • Stevensite

Clays and Clay Minerals; April 1990 v. 38; no. 2; p. 171-178; DOI: 10.1346/CCMN.1990.0380208
© 1990, The Clay Minerals Society
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