pressure
for hydraulic purposes. This ditch was extended to a point opposite the
mouth of Dalton Branch, where a fall of nearly 100 feet could be
obtained to hydraulic the bottom lands below. Another reason for the
construction of the ditch was the hope that by turning the creek from
its bed close to "In Situ Hill" the flow of water in the shaft on the
ruby matrix would be diminished and the surrounding mud become harder.
A 20-horsepower engine with a rotary centrifugal pump and bucket
elevator were installed to assist in sinking the shaft and driving a
crosscut from the bottom through the soft ground. The matrix in which
the ruby corundum occurs, and in which genuine rubies are said to have
been found, consists of hornblende gneiss and pegmatite in hornblende
gneiss. The pegmatite occurs in small streaks and lens-shaped pockets
from an inch or two to a foot thick, roughly conformable with the
bedding of the inclosing hornblende
gneiss.
Both the pegmatite and the hornblende gneiss are very badly decomposed
at the surface. The feldspar of the pegmatite has largely passed into
kaolin, while the hornblende gneiss has altered to the yellowish brown
earth characteristic of the saprolite of that rock, with hydromica and
black spots where small garnets have rotted away throughout. That this
weathering extends to a depth of over 30 feet is shown by the material
removed from a shaft of that depth. The strike of the country rock at
"In Situ Hill" is north of east, with a high dip to the southeast. A
dike of hard unaltered hornblende eclogite outcrops in the bottom of
the valley, a few feet north of the ruby matrix, and can be traced to
the east and west some distance. The hornblende gneiss saprolite
contains parallel streaks of mica-gneiss saprolite included in it.
In
some of the pockets of decomposed pegmatite translucent pink to lilac
colored corundum is very abundant, both in fairly large well-formed
crystals and in small fragments. Red and ruby colored corundum is less
plentiful, and but few crystals of gem quality have been found in the
pegmatite bodies so far. Portions of the hornblende saprolite inclosing
the pegmatite carry small translucent corundum crystals and fragments,
some of rich red color in small pockets of soft white material. These
were probably small masses of pegmatite which have decomposed, though
they might possibly represent the decomposition products of former
corundum crystals. From the few specimens of matrix seen by the writer,
it appeared that the corundum associated with larger bodies of
pegmatite is inclined to be of a lighter color—pink or lilac—than the
richer red stones in the hornblende rock alone, or where pegmatite is
less prominent.
INDIA.
Burma.—The
production of ruby, sapphire, and spinel by the Burma Ruby Mines
Company during the year ended with February 28, 1907,° amounted to
326,855 carats, valued at £95,540, as compared with £88,340 in 1906.
Of the total value of the output, ruby amounted to £93,023, sapphire to
£1,132, and spinel to £1,385. The net profits of the company amounted
to £15,160 after deducting a tax of £6,819 paid to the government of
India.' During the year, 1,890,944 trucks of ruby earth were washed, at
a cost of 7.7 pence per truck, as compared with 1,773,129 trucks at 8.1
pence in 1906.
o Eec. Geol. Survey India, vol. 36, pt. 2,1907. & Jewelers' Circ. Weekly, September 25,1907.
