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MINING
gem variety of the mineral cordierite. To
further enhance the gemstone potential
of the area, pegmatite dykes intrude the
Passmore metamorphic complex and
contain small blue aquamarine crystals,
gorgeous deep red garnets, and smoky
quartz. Pegmatites are particularly pro
-
spective for many gemstones because the
coarse-grained
igneous rock may contain
small cavities that enable late-stage gem
crystal growth. Star sapphires and other
gems are also found in alluvial gravels in
the Slocan River valley area.
Further south, between Salmo and
Creston, light blue to sky blue aquamarine
crystals are found within later-stage quartz
veins and pegmatites along the Shaw Creek
Stock. Aquamarine is also found in peg
-
matites northwest of Cranbrook along the
western
margin of the White Creek batho-
lith. Other places where aquamarines are
found
include McDame, Prince George and
near Atlin, northern BC. Sherry-brown
topaz crystals are commonly associated
with aquamarine.
What about emeralds in BC? Emeralds
and aquamarine are both varieties of the
mineral beryl. Beryl is an ore mineral for
beryllium, which is used in the aerospace
industry. The splendid verdant color of
the emerald variety of beryl is caused
by trace amounts of chromium and/or
vanadium in the beryl crystal structure.
Beryllium and chromium atoms are prac
-
tically incompatible in nature and only
under extreme
geological conditions can
they combine to form an emerald crystal.
Geologists have postulated where emer
-
alds may occur in BC. A single occurrence
of deep green
beryl is reported at Red
Mountain near Stewart. There are several
excellent papers describing "beryl belts"
where the elusive combination of beryl
-
lium and chromium may be targeted within
the province.
One of the best target areas
is where beryllium-bearing pegmatites or
granites interact with ultramafic chromium-
rich rocks. Other good targets are where
granitic stocks cut through black shales.
Emeralds are also found in mica-rich
reaction zones that occur at the contact of
pegmatites and quartz-tourmaline veins
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