Natural History.— Mineralogy. 201 
ore. No gold occurs in the first set of primitive rocks, and, with 
the exception of a great deposit of magnetic iron-ore in theprovince 
of Saint Paul, no other metalliferous minerals, A bed of 
quartz, with gold, occurs in the quartz-rock and quartzy mica- 
slate. This bed, which varies from an inch to six feet in thick- 
ness, is composed of quartz and schorl. Veins of quartz with 
gold also traverse this rock; and these, besides the gold, con- 
tain iron-pyrites, arsenical pyrites, and antimony. Some veins 
contain only kyanite. The slaty quartzose micaceous iron-ore 
contains gold, iron-pyrites, actynolite and kyanite ; also beds of 
quartz with gold ; beds of magnetic iron-ore, and of iron-gjance ; 
and also beds of brown iron-ore, chlorite-slate and talc-slate. 
The beautiful yellow Brazilian topazes, also beryl ? occur in 
nests and small veins enveloped in iithomarge, in the chlorite 
and talc-slates subordinate to the clay-slate ; also the rare euclase, 
and frequently large and beautiful crystals of iron-glance, with 
crystallized talc, rock-crystals with adhering topazes, topaz-crys- 
tals with included rock-crystals, and kyanite, encrease the inte- 
rest of these repositories. Beautiful red-lead spar or chromate 
of lead occurs in the potstone, and beds of iron-glance, upwards 
of 1000 feet thick, occur in some places. The transition rocks 
are clay-slate, common flinty slate, greywacke, greywacke-slate, 
and compact limestone. The sandstone named Quadersand- 
stein, often highly impregnated with iron, seems to be a predo- 
minating secondary rock. Hematitic brown iron-ore abounds in 
it, and it contains beautiful Wavellite. The Jura limestone, 
which occurs in abundance, contains fossil fishes, flint, echi- 
nites, and also rocks of the salt formation. The alluvial rocks in 
Brazil are of two descriptions: one kind occurs principally on 
ridges of mountains and upon their sides, the other in the bot- 
toms of valleys. The alluvium of the first kind, named in the 
country Tapanhoacanga , is composed of fragments of iron-mica 
and magnetic iron-stone, connected together by means of red or 
brown iron-ochre. It is often very rich in gold, contains beds of 
brown iron-ore, and large nests of Wavellite. The alluvial sub- 
stances of the second kind occur principally in valleys, and are of 
two principal varieties, the one, which is compact, is a conglo- 
merate of pieces of quartz cemented together by means of 
brown and red iron-ore, and which sometimes contains gold, and 
