92 
•EDWARD S. SIMPSON, B.E., F.C.S. t 
All three elements were discovered about fifty years 
ago and have since been prepared in the metallic state. 
They prove to be soft, white or gray, easily fused metals. 
No practical use has been found for any of them. One of the 
most remarkable properties of gallium is that whilst un- 
oxidised by exposure to air it will melt readily if held in 
the hand, its fusion point is so low (30°C.). The only 
compound of any of these elements put to any practical use 
is the nitrate of thallium used for determining the specific 
gravity of gemstones and other minerals. 
None of these metals has been recorded as yet from 
any mineral in this State, simply for lack of search. There 
is every reason to believe that they do exist here, merely 
awaiting careful search to be detected. 
Yttrium Group of Metals— Yttrium is a moderately 
common element, forming an essential constituent of many 
minerals, and also occurring in small quantities in a large 
number of others. It is invariably associated with small 
amounts of several other rare metals of similar character, 
viz. : — 
Dysprosium 
Erbium 
Thulium 
Ytterbium 
Lutecium 
Scandium 
Samarium 
Europium 
Gadolinium 
Terbium 
As long ago as 1794 a new metallic oxide was separated 
by Gadolin and subsequently named yttria. This, however, 
was not true yttrium oxide, but a mixture of that oxide 
with much oxides of erbium, etc. It was not till 1843 
that it was shown to contain the oxides of at least three 
metals — yttrium, erbium and terbium. During the last 
thirty years the further complexity of the original yttria 
has been shown, the latest new metal to be added to the 
list being Lutecium by Urbain and Welsbach, working 
independently, in 1907. 
As already stated, yttrium is an essential constituent 
•of many minerals of which gadolinite (silicate of yttrium, 
iron and beryllium), xenotime (phosphate of yttrium), 
euxenite (niobate, tantalate and titanate of yttrium, erbium 
and uranium), and feqgusonite (tantalate and niobate of 
yttrium, erbium and uranium) have already been discovered 
in this State. Certain cerium minerals of local occurrence 
also contain small percentages of this metal. 
Erbium oxide is known to form a considerable proportion 
(one-quarter to one-third) of the total rare earths in most 
yttrium minerals, including those in this State which have 
been examined in detail. It is known in other parts of the 
world as the main base of a single mineral, Sipylite. 
