Map India 2005 Geomatics 2005

fractures. Three sets of joints are common: N 45 0 E to S 45 0 W/70 deg vertical, N 10 0 W
to S 10 0 E /vertical and N 45 0 W to S 45 0 E/vertical
Mode of occurrence of Corundum
The mode of occurrence of Corundum (all varieties) in Gubbagurti area is in the
form of float, insitu and placers. Float deposits are observed in close proximity to the
primary occurrence and is mixed with soil cover or weathered zones of the rock or in the
colluvium mixed with quartz and it is very difficult to observe unless the eyes are properly
trained.
Insitu occurrence of corundum is noticed in association with felspathic rocks and
pegmatite emplaced into the structural planes of amphibolites. The contact between
felspathic rock and the garnetiferous amphibolites forms major insitu occurrence. The
dug material shows the presence of weathered pegmatite associated with amphibolite.
Petrographically corundum with lamellar twinning is associated with coarse grain
felspathic rock.
Placer concentrations are exploited along the Nalla courses. Expansive panning
of alluvium is observed and the recoveries are also encouraging particularly during rainy
season. It is vividly observed along the culverts where prospecting pits by the locals
amply justify the transportation of corundum from the upper reaches of the stream
system. The significant feature of corundum occurrence is along the structural trends,
which control the drainage pattern, and where colluvium is extensively associated with
pebbles of quartz. Placer accumulations with thickness of about 10 Cm. lying below a
thick soil cover of about 1m. spread over a large aerial extent is under active
exploitation.
Exploitation and Extraction of Corundum:
Corundum pieces are collected soon after the rains generally at the periphery of
the basic rocks as pyroxene granulites, amphibolites and schists. The detrital corundum
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