Fibrofebrite and Copiapite from Yetar Spring, near Chidlows. 79 
3 .— fibroferrite and copiapite from yetar 
SPRING, NEAR CHIDLOWS. 
By Rex T. Prtder, Ph.D., B.Sc., F.G.S. 
Read 14th October, 1941 : Published 21st May, 1943. 
Yetar Spring (Lat. 31° oG*o^ S., Long. 11G° 21-4' E.) is situated in the 
upper reaches of the Helena River some 51 miles S.S.E. from the junction 
of the main hTortham and York roads {see W.A. Govt. Litho. 2 /80). 
My attention was drawn to this locality by Mr. L. Burgess of Fauldings, 
Ltd., Perth, who collected encrusting material from the mound built up by 
this spring. This material, which Mr. Burgess gave to me for determination, 
proved to consist largely of a mixture of fibroferrite, copiapite, and melanter- 
ite. As this occurrence of fibroferrite was the first record of this mineral for 
Western Australia the locality was visited by Professor Clarke and myself 
in April of this year, and a closer examination of the occurrence was made. 
THE MOUND SPRING. 
The spring, situated on flat ground, several hundred yards south of the 
Helena, has built up a mound 1|- chains in diameter and about 15 feet high 
(fig. 1). The mound consists of a black peaty earth which is a greyish colour 
when dried. This material, on ignition, yields a greyish diatomaceous earth 
consisting entirely of diatom remains and delicate rods of amorphous silica. 
The latter are broken and do not show any pointed ends or a central canal 
and are therefore not sponge spicules — they may be silicified plant fibres. 
A partial analysis of this diatomaceous earth (dried at 100°C.) gave ; — 
0/ 
/o 
Loss on Ignition” ... 
21-85 
f^iCb 
69-71 
FcoOs 
3-46 
Rest ... 
4-98 
100-00 
Anal. : R. T. Prider. 
According to tlie owners of this property, the mound from which the spring 
issues has gradually increased in size, apparently by growth from below, 
during the forty years that it has been known, so that several enclosing fences 
have been destroyed. About LJ- chains wnst of the main spring there is another 
small spring and the ground surface over an area of about ten scpiare yards 
is slightly uplifted. 
The water from the spring is rich in solids (determined at 0'3077 parts 
per cent.) and qualitative tests indicate that chlorides are the dominant 
constituents with minor amounts of sulphates. The metallic ions present are 
mainly alkalies with lesser amounts of magnesium. No iron is present in 
the water, although in the channel through which the spring water runs over 
the surface of the mound there is a copious precipitate of flocculent iron oxide. 
The sample collected by Mr. Burgess formed an encrustation on the peaty 
diatomite in the vicinity of the channel draining the water from the top of the 
