Nigerite from Lixa, Near Felgueiras, Douro Litoral Province, Portugal

R. Van Tassel
Institut royal des Sciences naturelles de Belgique

Summary: Nigerite occurs in pegmatite as hexagonal crystals enclosed in mica or in association with lithiophilite, apatite and vivianite. Absolute hexagonal para-meters are a 5·67 and c 13·88 Å. Powder data are given. Forms {101¯3}, {101¯1} and {101¯0} present besides the well-developed {0001}. Density 4·25. Refractive index 1·80, birefringence about 0·005, negative optical character. The chemical composition is studied by means of chemical, X-ray fluorescence and optical spectrography methods.

Mineralogical Magazine; 1965 v. 34; no. 268; p. 482-486; DOI: 10.1180/minmag.1965.034.268.42
© 1965, The Mineralogical Society
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