The Rare Earths: Their Occurrence, Chemistry, and TechnologyLevy, Stanley Isaac
Science
The Rare Earths: Their Occurrence, Chemistry, and Technology
Levy, Stanley Isaac
Rare earths
Monazite also occurs to a considerable extent in the diamond sands and
gold-bearing sands of many of the interior provinces. In Minas Geraes it
has long been known to occur at the celebrated mining centres of
Diamantina and Ouro Preto, where xenotime and other rare earth minerals
are also found; it is also known at various localities in the
surrounding mining provinces of São Paulo, Goyaz, and Matto Grosso. More
recently, extensive inland deposits have been found by Freise, in the
province of Espirito Santo.[122] In the plateau-basin of the Muriahé and
Pomba rivers he found a sand known locally as ‘catalco’ which carries an
average of 2·1 per cent. of monazite and a gold-content of 1·75 grams
per ton. In the Aymoré’s mountains he found monazite, both massive and
granular, in pegmatite veins in granite; analysis showed a thoria
content of 9·23 per cent., which is very high. These deposits would form
a very valuable and extensive source of thoria, if the difficulties of
transport could be overcome.
[122] _Zeitsch. pr. Geol._ 1909, ~17~, 514; _ibid._, 1910, ~18~, 143.
At present, as stated above, only the beach deposits are worked. The
Brazilian Government has laid a very heavy tax on all monazite exported;
it is stated[123] that the German Thorium Syndicate pays 50 per cent. of
its profits in royalties to the Government. In spite of this, the high
quality of the sand and the low cost of transport have enabled this
combine to lower the price of thorium nitrate to a point at which the
Carolina sands cannot be worked, and it appears probable that the
world’s markets will be supplied for some time, at least, entirely from
Brazil. The methods employed in working the sand are similar to those
already described.
[123] _U.S. Geol. Survey_ (_Minerals_), 1906, p. 1195.
In the last few years monazite deposits have been found in various
places, notably in Australia, India, and Ceylon. In the latter locality
it occurs sparingly in the gem-gravels, in association with the much
more valuable thorianite and thorite, but the supply is uncertain, and
the minerals cannot be worked regularly. In Australia it occurs in
Victoria and in Queensland. In Victoria the deposits are poor in
monazite--about 0·025 per cent.--so that working is not profitable. In
Queensland it occurs in beach sands on the southern coast, with gold,
platinum, and cassiterite; there seems to be no reason why these
deposits should not be profitably worked when sufficient labour is
forthcoming. It also occurs in North Queensland, on the Walsh and
Tinaroo mineral fields; here it is found massive and granular in veins
in granite, associated with wolframite, molybdenite, and cassiterite.
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