Portal de Periódicos da CAPES

Nigerite from Lixa, near Felgueiras, Douro Litoral province, Portugal

1965; Volume: 34; Issue: 268 Linguagem: Inglês

10.1180/minmag.1965.034.268.42

2515-821X

René Van Tassel,

X-ray Diffraction in Crystallography

Summary Nigerite occurs in pegmatite as hexagonal crystals enclosed in mica or in association with lithiophilite, apatite and vivianite. Absolute hexagonal parameters are a 5·67 and c 13·88 Å. Powder data are given. Forms and 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.