be
scratched with a knife. The color varies from emerald green through
pale green, light blue, and golden yellow to white and pale pink. The
crystals are generally hexagonal prisms, many of them striated
vertically, and most of them terminated by a single flat plane at right
angles to the long axis of the prism. Some pyramidal terminations also
occur. There is no marked cleavage, only an imperfect one parallel to
the basal planes. Beryl is fusible only with difficulty and is not
attacked by acids.
OPAQUE BERYL.
The
commoner varieties of beryl are light blue or green in color, -and are
opaque, though portions of some crystals are transparent and may even
yield gems. Opaque crystals are quite common in most of the coarser
pegmatite deposits of Maine, where they occur as more or less regular
prisms embedded in the solid pegmatite. Some of these reach remarkable
dimensions; one found in the Maine Feldspar Company's quarry at Mount
Apatite in Auburn was described as having a diameter equal to that of a
hogshead. One from the Noyes gem mine in Greenwood, Oxford County, was
so large that a man could barely reach around it with his arms. From
Acworth, N. H., one crystal 6-1/4 feet long and another estimated to
weigh over 2-1/2 tons were quarried. A peculiar beryl from Auburn is described by Kunz as follows: °
In
the state cabinet in Albany, N. Y., is a curious beryl found by S. C.
Hatch at Auburn, Maine. It is of imperfect structure and broken
diagonally across, showing the structure to advantage. It is
8-4/5inches (30 centimeters) high, 8-3/5 inches (22 centimeters) wide,
and has 50 different layers, 25 of beryl, the remaining 25 of albite,
quartz, and muscovite. All the corners of the hexagonal prism are
carried out in full, giving the beryl an asteriated appearance and making it a striking and interesting specimen.
The
opaque varities of beryl are of little commercial value, though prized
for museum collections when they show perfect crystal forms.
EMERALD.
Transparent
beryl of deep-green color is the gem emerald, but it must not be
confused with the oriental emerald, which is a green variety of
corundum. Emeralds are of rare occurrence in the pegmatite deposits of
Maine. One crystal of light grass-green color embedded in quartz was
observed by the writer at the Dunton gem quarry in Newry, Oxford
County. It was a prism half an inch across and 1-1/2 inches long but
was so badly fractured as to be valueless for gems. Parker Cleveland b mentions having seen several emeralds from Topsham, Sagadahoc County, of a lively green color and
o Kunz, G. F., Gems and precious stones, pp. 91-92. b Mineralogy and geology, 1822.
63096°—Bull. 445—11-----10
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