284 PROCEEDINGS OF SECTION C. 
masses of gabbro and pyroxenite have been largely con- 
verted into serpentine. Owing to the disappearance of the 
felspars, it is difficult to determine whether our serpentines 
were originally gabbro or pyroxenites. Analogy suggests 
the derivation from pyroxenites and ‘peridolites. 
The rock generally is intrusive in the Silurian slates and 
sandstones. These intrusions may be seen very plainly im 
the Heazlewood district, along the road between the Arthur 
River and the Heazlewood Bridge, at the Magnet Mine, 
&c. Later, the Devonian granite has intruded in the basic 
rocks, as shown by the amphibolites at the Heazlewood and 
the gabbro-diorite at Mt. Agnew. 
The freshest sample of the rock hitherto met with is from 
24 miles west of Ringville, where it is as well preserved as 
any of our Mesozoic dolerite. Some very fine rocks, how- 
ever, are obtainable at the Heazlewood, where gabbro proper 
frequently varies into a norite and olivine norite. On 
the north slope of Mt. Bischoff aserpentinised gabbro occurs, 
with rhombic pyroxene, and interstitial quartz = quartz 
norite. 
The metamorphic modifications of gabbro may be studied 
to advantage at the Heazlewood and Mt. Agnew, and ap- 
parently also at the Rocky River, where magnetite beds, 
with nickel and -pyrrhotite, are enclosed in hornblende 
schists and gneissose amphibolites (with zobtenite). 
One result of metamorphic agencies is the development 
of the albite-zoisite mixture, called saussurite, which replaces 
the felspar. This change is apparently a phase of regional 
metamorphism. Some very pure milk-white saussurite 
occurs in loose blocks on the Heazlewood River. A very 
singular saussurite-gabbro occurs in the Anderson’s Creek 
serpentine area, consisting of long prismatic brown horn- 
blende, set in a white saussuritic matrix. This idiomorphic 
hornblende must be a secondary development, and the rock 
will have to be called a gabbro-amphibolite; there is no 
shistose structure in it, however. 
The rock at the Comstock Quarry, near Zeehan, is gabbro- 
diorite ; the pyroxene has been converted into hornblende, 
the gabbroid structure of the rock still remaining. The 
gabbro all along the Trial Harbour Road, at the foot of 
Mt. Agnew, shows this kind of metamorphism. The new 
mineral is pale bluish green, and often shows the cleavage 
lines of hornblende. It must be remembered that this is 
the contact-line with the intrusive granite of Mt. Heemskirk. 
The gabbro at the Heazlewood, along the line of contact 
with the great Magnet-Meredith graniterange, presents many 
amphibolitic varieties, often losing its gabbroid structure and 
