84 
A. r>. I^DWARDS. 
(JIaiK'ophaiie is n^conlf’d <*lnaf]y from motamorpliie rocks, and its occurrence 
as an alteration ])roduct of a doleritn is unusual, particularly since, the doleritcs 
in this region are for tlu^ Ttiost part fr(‘sli and un-metamor]jhos(Kl. The presence 
of pyrite and carhonatt‘s in the rock suggests that it lias undergone local 
ni(dasonuitism, or possibly autopnemnatolysis. 
2. l''wo-p}jrox'ene itmivshti -imsalt.s. 
[.‘1749t from I mile imrtlcwi'st of ('amp F.l>. :2S. junctio!! of Alainite (’n^ck and 
(’liamlcy Ihvrr (analysed). 
|:^7(il|, from the CahU'c Pdver, d miles west of F.B. 34. 
j37(>3|, fnmi the Harding Ihinge, S(M> fia'l 1k4ow the summit, and 1 mile from 
K.P>. 43. 
137(m]. from the !lai'<ling Itange. l.l(M) feet below the summit, and 1 mile fiom 
F.li. 43. 
1 3773], from th(* summit of .Mt. Trevor. 
i72h4j, from a dyke in .sandstone, rpiuu’ Isdell River. 
ddiis small group of glassy basalts has a distincti\'e appearance under the 
mi(n‘()seop(‘ ( Plat(‘ 1., Fig. 2). Both pyroxeiu' and plagiotdase occur as (dongated 
laths (1*5 to 1*0 mm. long a-ixl 0*02 ta> 0*d5mm. wide, and show a tendency 
to foi-m stellat(‘ (dustiM's in tin* dark glassy has(a 4'he pyroxene sometinw^s 
occurs in radiating s}i(>a,vi‘s. Two xariidies arc pi(‘S(‘nt. Ono has ( ]- ) 2\' 
— , so tluit it is a pigeoiiite. The oHier has ( f ) 2V' greater than 45'^. 
and is pi‘oha()l\' aiigite. In most of tlu^ speeinuais tlu^ pyroxeiu' latlis were 
just b(‘ginniug to erystalli/.(^ wlu'ii the rock was chilhsl, and indistiiud trichytes 
of pyrox(‘ne can madt^ out in 1h(^ dark glassy l)as(‘. Thesis trichyt('S Paid 
to a ra<lial arrarigemcait, suggt^stive. of colourless horulilende lilin's, hut ai'(‘- 
prov(‘d to be [)yroxeue by their lai’gt^ (extinction angles, which range up to 4(1°. 
Tlue plagioelasie laihs began to eryslHlli/*(* before the ]);v’roxeiie, and some 
of tluau are of micropluerjoi-ryst size, dduw are largely altei'j'd to vvhlt(' mica, 
chloriRe, aiicl sometirru's c])idote, hut occasionally they still sIjom' broad lamellar 
twinning, with an extinelion angle in the symm(*trieal zoiu* of about 20", so 
that they consist of and(*siu(e of a comi>osif ion about AlidO. In ('ach scx’.tioii 
there are one or two niiero|)h(‘nocrysts of alt<‘r('(i oli\'ine, which i‘(>tain tludr 
idiomorphie outlint* to sonue (‘xtent (Plate I., Fig. 2). ddie atamdant glass is 
gn'yish and opacjue, hut urubu* liigh maguilicatiou it resolves into a ufdwork 
of [>yrox('U(‘ microlites. Iron orc^s ane gtaierally absent. 
Tcextiirally thc'se rocks lia-ve considerabh' attinity with tholeiites, but 
mineralogieally tli(\y aine I’chifed to the andesites. A elu>mieal analysis of 
[3749] (d’ahh' II., No. I) iiulicates that tlu* rocks an^ liasaltic in com])osition. 
hilt midwfiy, as it W('re. betwfeen th(e thoh'iities ])i*oper and the andesites. 
The Al.iO;p Na^O and K.>() conhuits ar(’ too high for tholeiit('s, just as the 
amk^sine hdspar is too acid. Tlu>s(‘ ftmtures also distinguish this group of 
basalts from Ihe t wo-pyrox<ui(' (lol(U‘it<‘s of (Jroup I. 
3. A r)desin(’-h(tsalts. 
137t)()|, from the (hIuc of tidal w{il»-r. 9 mil(‘.^ south-west from F.B. 4t. 
|377t)l. from Camp F.B. o.’k south side (»f IIk* (’ole River. 
[3772|, from a lull near Mt. byell, and :{ mile.s north-east of F.P>. 57. 
|3779|, from 3 miles math of F.P>. 79. at .\apier Broome Bay (analy.sed). 
13777], an epidositized speeiiium from tlu* same locality as j377(>| (analysed). 
j377S|. from the same locality as |377ti|- 
[724()j. from tlu* Harm River, 
|7271], a dyke, from near Mt. .lo.seph. 
The sp(K*im 0 ns eom]irising this group are coarser grained than the basalts 
of Group 2. and contain less glass (Platt' 2., Fig. 3). The felspar is a more 
acid andesine, about Ab-,,, occurring in laths that He at all angles to ono an- 
