RT Journal Article
T1 Macroscopic palygorskite from Lisbom Volcanic Complex
A1 Súarez Barrios, Mercedes
A1 García Romero, Emilia
AB The palygorskite of the Volcanic Complex near of Lisbom (Portugal) is particular both in the size of the fibres and inchemical composition. It appears as veins of very pure mineral. From hand specimen and optical observations it can be described asa macroscopic palygorskite. The crystals are large with exfoliation traces of several hundred microns to few millimetres in length. Inthin section, this palygorskite is colourless, translucent, negative biaxial, with positive elongation and parallel extinction. Theoptically homogeneous fibres and laths are shown by the selected area electron diffraction to be composed of aggregates of muchthinner fibres rotated differently around the c crystal axis which represents their common elongation direction. The chemical formulaobtained by the X-ray EDS is Si8.02O20 (Al1.91 Fe0.04 Mg 2.01) (OH)2 (OH2)4 Ca 0.01 Na 0.07 4(H2O) very close to the ideal formula of apureMg-Al palygorskite,with almost no octahedral Fe, and noAl in tetrahedral sites. The cell parameters are a0 or a0 sin q = 12.64 A° ,b0 = 17.84 A° and c0 = 5.3 A° .
PB E. Schweizerbart'sche Verlagsbuchhandlung
SN 0935-1221
YR 2006
FD 2006
LK https://hdl.handle.net/20.500.14352/50677
UL https://hdl.handle.net/20.500.14352/50677
LA eng
DS Docta Complutense
RD 5 may 2024