A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM 11
of platinum have been noticed associated -with the gold obtained from native workings at
Bonai, in India. 28 Platinum, and iridioplatinum were discovered in Burma, in 1831,
in the auriferous sands of the Ava. The occurrence was described by J. Prinsep, A. Faber,
It. Romania, and H. Burney ; and M. F. Heddle proposed to call the metal from this
locality avaite. Platinum occurs associated with gold in the Irawaddy River, and it has
been obtained commercially at Myitkyina ; and it has been located in the iridosmium in
the auriferous gravels of the rivers draining the Patkoi Ranges on both the Assam and the
Burma sides. Platinum was also discovered in south-eastern Borneo in 1831, Jn the gravels
of Gunung Lawack ; and, according to T. Posewitz, 24 it is now obtained as a by-product
of the gold-washing in the province of Tanah-Laut. The platinum is here associated with
osmiridium, and gold. The mineral laurite, (RU,OB)S2, occurs in these deposits. L. Hundeshagen
also described the occurrence of platinum in the diamond placers, "west and southeast
of Borneo. The Borneo platinum was examined by M. Bocking. According to
L. Hundeshagen, platinum occurs in Sumatra at Singenggnu, east of Sipongi, along with
gold, wollastonite, and grossularite m limestones and schists near intrusions of grano-diorite
and augite-diorite. E. Hourteau discussed the platinum occurrences in New Caledonia.
Africa.—G. Aim6 26 observed traces of platinum in the galena of Algiers ; K. Aekermann,
in grains in a creek at Gondoko, and at Missiva in the Sudan and Upper Senegal ;
L. Duparc, L. Duparc and E. Molly, and F. Hermann and O. Giinther, in Birnir, Abyssinia ;
N. R. Junner, in Sierra Leone ; R. P. Rothwell, in the bed of the River Uello, in the
Katanga district in the Congo Free State ; and A. Lacroix, as a by-product in the alluvial
gold mining on the Vatana River, near Ambia, in Madagascar. Traces of platinum have
been also reported in the auriferous gravels of Fenerive, Marolambo, and Vandrozo, in
Madagascar. The subject was discussed by L. Duparc, and L. Duparc and co-workers. The
gold-platinum deposits at Ru we, in Katanga, were described by P. V. Brande.
A. E. V. Zealley *« located platinum in the conglomerates and gravels of the Soinabuba
Fields, near Gwelo, in Rhodesia. The country rock is serpentinized dunite. The deposit
is capped by a ferruginous, siliceous gossan. The ore yields 3 ozs. 12 cwts. of platinum
per ton, and 7 ozs. of osmiridium per ton. B. Lightfoot, and H. B. Maufe also noted gold
and platinum in a reef in the great dyke of norite at the head of the valley drained by the
River Umtebekwe. The platinum is found only in notable quantities in those areas of
the dyke where felspar-rich norite is present. According to P. A. Wagner, there are
large reserves of platinum in. South Africa, principally in the Transvaal. The platinum
metals occur in the most diverse circumstances, and in rocks ranging in geological age
from the most ancient to the most recent. W. Bettel noted the metal in the black sands
from the battery " clean-ups " on the Rand at KIerksdorp, and other gold-mining districts,
and in the residual slimes at the Rietfontem mines. A. Hall and W. A. Humphrey observed
that samples of chrotnite from Kromdaal, near Rustenburg, and from the Secoeoeniland
deposits may contain 1 to 1 £ dwt. of platinum per ton. The platinum metals in the
Transvaal occur in the ultra-basic and basic rocks about Uitkomst, Freezburg, and Messina ;
in the auriferous conglomerates of Witwatersrand, and the Black Reef in JKlerksdorp
district; m the norite zone of the Bushveld; and m the igneous complex—a vast body of
plutonic and volcanic rocks in the central part of the Transvaal. According to P. A. Wagner,
the platinum here occurs in
1. Oreumotectic deposits formed by segregation from the parent norite magma,
and occurring in the acid quartz-bearing differentiates of the norite magma.
11. Orthoteetic deposits formed by direct segregation from the parent norite
magma.
A. Deposits in which platinum is associated with magmatic nickel-copper-iron
sulphides in norite, pyroxenite, and harzburgite.
(a) In the upper part of the norite zone, e.g. (i) Deposits of the Blaauwbank
type in which the ore-bearer is quartz-bearing anorthositic
norite. (ii) Deposits of the Stulpoort Park type in which the
ore-bearer is a medium grained, spotted norite rich in felspar,
(iii) Deposits of the Minsk's Claims type, Lydenburg District,
in which the ore-bearer is a rather coarse-grained diallage norite
rich in felspar,
(o) In the lower part of the norite zone, e.g. (iv) Deposits of the
Merensky Horizon tyj>e occurring above and below the main
horizon in the Lydenburg District. (v) Deposits of the
Merensky Horizon type as developed in the Rustenburg, Pretoria,
Lydenburg, Pietersburg, and Potgietersrust districts ; the ore
bearers are pseudo-porphyritic pyroxenitic diallage-norite,
felspathic, pyroxenite, felspathic harzburgite and ehromitite.
(vi) Deposits of the Tweenfontain type, Potgieterscrust District
in which the ore-bearer is a fine-grained pyroxenitic diallagenorite
emerging into coarse-grained felspathic bronzitite and
bronzitite. (vii) Deposits of the VaIk fontein type, Rustenburg
District, in which the ore-bearer is bronzitite.
B.—Chromitite deposits.