12 PLUTONIC ROCKS,—-CASE IT, 
*117. Decomrosep Rock. 
Map No. R 8. 
Moonee Ponds. 4 sheet 1 N.W. 
Occurs in Upper Silurian; it resembles 
an older basaltic clay, with patches of a 
greenish, decomposed, probably magne- 
sian mineral. 
#118, FELSPATHIC ROCK. 
Portland. 
A white, felspathic base, with em- 
bedded crystals of quartz and glassy- 
looking felspar. 
Presented by E. Dacomb, Esq. 
*119. Scnort ROCK. 
Mount Singapore, Corner Inlet, 
Black, fine-grained rock, consisting 
of tourmaline and quartz. Occurs tra- 
versing granite, and has been opened as 
an auriferous lode. 
*]20. Granitic Quartz Por- 
PHYRY. Map No. R 94. 
Bach Creek, east of Spring Plains. 
4 sheet 51 S.W. 
Consists of a white, finely granular 
base, in which are embedded crystals 

of quartz and felspar, and a very little 
white mica. It commences at the granite 
boundary on Dr. Baynton’s station, can 
be traced for about 4 miles due north 
(magnetic), and is most likely a con- 
tinuation of the dyke that runs through 
Heathcote. (See Note following speci- 
men No. 97.) It is sometimes mottled 
brown, red and white, and to the north 
loses its mica. It is sometimes yery 
hard, but apparently decomposes easily. 
In places along its course the Lower 
Silurian rocks rest on it in cappings or 
outliers, 
121. QUARTZ CRYSTALS. 
Map No. M 26. 
Same locality as last. 
A combination of the double six-faced 
pyramid and hexagonal prism. These 
crystals are liberated by the decompo- 
sition of the rock, and may be collected 
from the surface gravel along the out- 
crop of the dyke. 
PORPHYRIES. 
1. EARTHY FELSPAR TRAP. 
Map No. Ra 29. 
Lot3, parishof Newham. sheet 
6 N.W. 
Grey, earthy buse, with embedded, 
rounded fragments, probably decom- 
posed felspar. 
2, FELSPAR TRAP. 
Map No. Ra 25c. 
Brock’s Monument, N.E.of Mount 
Macedon, } sheet 6 N.W. 
Partially decomposed felspar base, 
with crystals of semi-transparent fel- 
spar, and speckled with minute, black 
marks. (Sce “Building Stones,” No, 
20.) 
3. FELSPAR PoRPHYRY. 
Map No. R 52. 
Hill between Rochfort and New- 
ham. sheet 5 S.W. : 
Brown base, with scattered, glassy- 
looking felspar crystals. (See “ Build- 
ing Stones,” No. 18.) 

*4, FELSPAR PORPHYRY. 
Map No. R 48. 
Dividing Range, north of Newham. 
4 sheet 5 N.W. 
Fine-grained, granitic base, with em- 
bedded felspar crystals. Occurs in 
granite. (See “Building Stones,” No. 
19.) 
5. FELSPAR PORPHYRY. 
Map No. Ra 27b. 
Dryden’s or Hanging Rock. Lot 6, 
Newham. } Eeer 6 N.W. 
Light-grey base, speckled with black, 
with embedded felspar and quartz crys- 
tals, and patches of yellow, decomposed 
AER (See “Building Stones,” No. 
22. 
Note—The “Hanging Rock” is a 
peculiar isolated outburst of felspar trap, 
of a light color, divided by numerous 
joints into rudely columnar forms, 30 
to 40 feet in height, and exhibiting its 
structure well displayed in large cir- 
cular and funnel-shaped cavities, which 
are abundant throughout thie mass. 
Those marked with an * occur as dykes (Elvans), 
