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Jeffrey Mine/Black Lake Mine Page 1
The asbestos deposits in Quebec are interpreted as part of an
'ophiolite sequence', sheets of oceanic crust smashed up against
the North American continent during a continental collision in
the Taconic orogeny about 490 million years ago. Hot water
circulated through the pyroxene and olivine rich ultramafic rocks
in the sequence during this process, transforming those minerals
into serpentine. The fibrous form of serpentine, chrysotile, was
deposited in fractures in the ultramafic rocks as cross fiber veins
where the chrysotile fibers occur at a high angle to the vein walls,
or as slip fiber veins where the fibers occur parallel to the vein
walls. The veins may be up to four inches thick. The mines devel-
oped in the deposits are world famous for grossular and vesuvian-
ite specimens. They also produce extraordinary pectolite, prehnite,
diopside, and brucite. These pages include a variety of specimens
from the mines at Asbestos and Black Lake.
M1564
GROSSULAR
Jeffrey Mine,
Asbestos, Quebec, Canada
Transparent grossular crystals on granitic
matrix.
.
Specimen size - approx. 12.5 cm. X 7.0 cm. X 5.0 cm.
M1716
SERPENTINE after AMPHIBOLE
Jeffrey Mine,
Asbestos, Quebec, Canada
A 'hornblende' crystal replaced by serpentine.
Specimen size - approx. 2.5 cm. X 1.7 cm. X 1.5 cm.
M1978
VESUVIANITE
Jeffrey Mine,
Asbestos, Quebec, Canada
A 'cross' of vesuvianite.
Specimen size - approx. 3.8 cm. X 2.9 cm. X 2.3 cm.
M0743
GROSSULAR
Jeffrey Mine,
Asbestos, Quebec, Canada
A cluster of gemmy, green grossular dodeca-
hedra.
Specimen size - approx. 3.5 cm. X 3.0 cm. X 2.0 cm.
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