26 
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Cretaceous. 
<2 ^ 
Jurassic. 
*S 
R« 
e 
Ri 
Carboniferous. 
Devonian. 
r Chalky limestones with flints, sand, ferruginous 
} sandstones, limestones, clays, micaceous clays, 
(. conglomerates, and coal seams. 
r Oolites :—Oolitic limestone, clay ironstone, fer- 
j ruginous sandstone, grits and conglomerates. 
1 Lias :—Ferruginous and variegated limestones, 
C clays and ironstones. 
f f Upper : —Sandstones, grits, conglomerates, and 
shales, with small quartz veins, and nodules 
of ironstone. 
Lower: —Limestones variously coloured, mostly 
hard and often magnesian limestones, mud¬ 
stones, fire clay, micaceous clays and shales, 
with iron pyrites, gypsum, and coal seams, 
caleite, agate, calcedony, and jasper veins, lead, 
zinc, and copper ores. 
f Sandstones, coarse grits, conglomerates, shales, 
-) slates, and hard limestones, with veins of agate 
C and calcedony, and micaceous iron. 
C Clay-slate, limestones, marble, dolomite, sand- 
Silurian. ) stones, quartzites, and conglomerates, with 
J veins of quartz, caloito and metallic ores and 
v. gold. 
( Crystalline limestones, sandstones, grits, quartz- 
; itos clay-slate, and sandy flags, with numerous 
) veins of quartz and calcite, gold, copper, lead, 
k and iron ores. 
^Marble, quartzites, altered grits, mica slate, 
mica schist, chloritic schist, hornblend schist, 
talcose scliist, garnet rock, gneiss, and granite, 
with numerous quartz reefs and mineral veins. 
This is the principal gold-bearing formation. 
Igneous. 
Volcanic. Basalt, dolerite, volcanic breccia, and obsidian. 
Plutonic f Biorite, feldstone, amygdaloids, syenite, granite, 
l porphyry. 
The Igneous rocks are of all ages, resulting from the solidification of molten 
matter which has been forced upwards from the interior of the earth, tilling 
fissures it has formed, pre-existing faults, or has been ejected from vents at the 
surface. 
They are usually divided into two classes, according to the circumstances 
under which they have become solid; those which have cooled down on or near the 
surface are called volcanic, and those that have solidified at some depth plutonic. 
They are often composed almost entirely of silica, and seldom contain less than 50 
per cent, of that mineral. 
Mineral Veins. 
Cambrian. 
Archaean , 
Crystalline. 
Mineral veins are deposits of mineral matter that occur in rocks of all ages, 
usually in faults, but sometimes in other fissures, in both stratified and eruptive 
rocks. Those containing metallic ores are termed lodes, occurring principally in 
the metamorphic archaean rocks at or near their junctions with plutonic rocks. 
Mineral veins may be divided into the following classes: — 
True Veins, sometimes called Right” or “ Fissure” lodes. This class of lode 
is best defined as a fissure of indefinite length and depth filled with a mineral 
substance, which if rich in a metallic ore would be called a lode, or rich in gold a 
reef. Veins of this class are supposed to have been caused by movements of the 
earth’s crust, and therefore probably extend for a considerable depth. The walls 
of true veins are generally striated, showing that a movement has taken place. 
Gash Veins arc not true fissures, as no dislocation has taken place in the 
earth’s crust, but are simply cracks infilled with mineral matter, and although 
