EVALUATION OF VEIN QUARTZ, MONTGOMERY COUNTY, NORTH CAROLINA FOR ITS SUITABILITY AS A QUARTZ RESOURCE

1
EVALUATION OF VEIN QUARTZ, MONTGOMERY COUNTY,
NORTH CAROLINA FOR ITS SUITABILITY AS A QUARTZ
RESOURCE MENSAH-BINEY, Robert, North Carolina
State Universitys Minerals Research Laboratory,
180 Coxe Ave., Asheville, NC 28801, REID, Jeffrey
C., North Geological Survey, 1612 Mail Service
Center, Raleigh, NC 27699-1612. Stock work vein
quartz 20 kg samples from metavolcanic rocks
from Montgomery County, North Carolina, were
evaluated for their quartz resource
suitability. Preliminary processing evaluation
and chemical analysis of the quartz concentrates
from the two samples indicated low impurity
levels to justify further chemical treatment to
produce ultra-high purity quartz. The processing
steps involved crushing, grinding to produce 60 x
140 mesh, flotation to remove mica, iron minerals
and feldspar impurities, magnetic separation of
the clean quartz, sizing and hydrofluoric /
hydrochloric acid leach to produce ultra-high
purity quartz product (Iota Grade). The chemical
analysis of the quartz concentrates before and
after leaching is shown in the table below
(unleached product is after magnetic separation,
leached product is after leaching with HF/H2SO4).
Although chemical leaching resulted in
significant reduction in Fe and Mg, the impurity
level for Al, Ca, Na, K was too high for
ultra-high purity quartz. Additional process
evaluation is needed to remove additional Al, Fe,
Ca, K, and Na to produce high-pure quartz
(Quintas Grade). Granular high purity quartz
(HPQ) is used in the manufacture of optical
glasses and for high purity silica glasses for
semiconductor silicon in silicon computer and
memory chip production (high purity crucibles for
growing the silicon), for high intensity lighting
applications and for standard and fiber optical
components. HPQ chips (lascas) are used in the
manufacture of piezo-electric quartz crystals
(cultured quartz). Some of the lower purity HPQs
are used in the ceramic industry for high heat
intensity applications such as the heating tile
for the space shuttle. The quartz composition is
shown in the table below. No gold was detected at
the ppb level in three composite bulk samples or
one duplicate bulk sample.
Above - Outcrop sample displays primary
hydrothermal plumbing and at least three
generations of quartz.
Above outcrop and outcrop detail of example
quartz exposure in Montgomery County, NC.
Below location map showing location of
Montgomery Co. North Carolina and generalized
geology from the Geologic Map of North Carolina
(1985).
Left table shows chemical analysis before and
after leaching.