Note on the Occurrence of Thorite at Alter Pedroso (Portugal). Report No. 29; NOTA SOBRE UMA OCORRENCIA DE TORITE EM ALTER PEDROSO. Memoria No. 29.
- Author
- Pacheco, J. T.
- Published
- [Place of publication not identified] : [publisher not identified], 1960.
[Oak Ridge, Tennessee] : [U.S. Atomic Energy Commission], 1960. - Physical Description
- microopaque : positive ; 8 x 13 cm
- Additional Creators
- Gomes, R. A. D.
- Language Note
- In Portuguese.
- Summary
- The first known occurrence of thorite in Portugal is reported. The mineral was found as small dark reddishbrown euhedral grains scattered in a soil sample from the hyper-alkaline syerdte region of Alter Pedroso, in prospecting for radioactive materials. Zircon, riebeckite, aegirine, feldspar, biotite, magnetite (all of these common minerals of the hyper-alkaline syenite), and a few other urddentified minerals were found in the soil associated with thorite. This suggests the weathering of a local pegmatitic differentiation of the syenite as the origin of the thorite. Microscopic examination shows the mineral to be only partially metumict, and it is probably altered to a variable degree. Euhedral grains are constituted by several nearly colorless anisotropic nuclei (n/sub p/ near 1.69, n/sub g/ near 1.71, and sometimes anomalous B+ with variable 2V averaging 10/sup 0/) surrounded by a golden-brown isotropic material (n about 1.67). Specific gravity determinations were somewhat impaired by zircon inclusions and led to a value of 4.79. The chemical composition was determined by emission and x-ray fluorescence spectrography and shows a high yttrium content. A partial semiquantitative analysis gave the following results: ThO/sub 2/ (58.0%), SiO/sub 2/ (14.5%), Fe/sub 2/O/sub 3/ (2.5%), Y/sub 2/O/sub / 3>i (2.5%), CaO (l.1%), U/sub 3/O/sub 8/ (0.5%), and PbO (0.2%). The elements Be, Mg, Al, Mn, and P were also detected. X-raypowder patterns obtained before and after heating the sample to 1000 ts C for 1 hr in air confirmed the mineral to be only slightly metamict and showed that the tetragonal phase still prevails above 950 ts C. Calculations based on these patterns led to a tetragonal unit cell with a/sub 0/ = 7.05 0.01 A, c/sub 0/ = 6.27 0.01 A, and c/sub 0//a/sub 0/ = 0.889. (auth).
- Report Numbers
- NP-9826
- Other Subject(s)
- Aegirine
- Aluminum silicates
- Aluminum
- Amphiboles
- Anisotropy
- Beryllium
- Biotite
- Calcium silicates
- Color
- Crystals
- Density
- Europe
- Feldspars
- Fluorescence
- Geology, mineralogy, and meteorology
- Grain size
- Hornblende
- Igneous rocks
- Impurities
- Iron oxides
- Iron silicates
- Lattices
- Magnesium silicates
- Magnesium
- Magnetite
- Manganese
- Mica
- Microscopy
- Minerals
- Oxides
- Phosphorus
- Portugal
- Potassium silicates
- Powders
- Prospecting
- Qualitative analysis
- Quantity ratio
- Riebeckite
- Silicates
- Sodium silicates
- Spectroscopy
- Spinels
- Syenites
- Thorite
- Thorium oxides
- Thorium silicates
- Uranium oxides
- X radiation
- Yttrium oxides
- Yttrium
- Zircon
- Zirconium silicates
- Collection
- U.S. Atomic Energy Commission depository collection.
- Note
- NSA number: NSA-15-009180
OSTI Identifier 4099835
Research organization: Portugal. Junta de Investigacoes do Ultramar, Lisbon.
View MARC record | catkey: 41356427