100 PEGMATITES AND ASSOCIATED ROCKS OF MAINE.
as
a constituent of a pegmatite mass, and it. probably occurred in
pockets. The minerals were probably dislodged, by the action of glacial
ice, from a decomposed pegmatite ledge somewhere on the flanks of Sugar
Hill and were subsequently deposited in their present position at the
base of the hill. Prospecting on the hill northwest of the beryllonite
locality may eventually disclose the source.
The
locality was first worked by E. D. Andrews, of Albany, who, in
searching for smoky quartz, found an unknown mineral, which was later
identified by E. S. Dana in 1888 as a new species and called
beryllonite. Its mineral characters have been fully described by Dana
and Wells.0
Harndon Hill.—A
well-known topaz locality is located on the summit of Harndon Hill, in
the southwestern corner of the town of Stone-ham, within one-fourth
mile of the Stow line. It was opened in the early eighties by Nathan H.
Perry, of South Paris, and worked intermittently for a number of
years, but at the time of the writer's visit in September, 1906, had
been practically idle for over ten years. The workings consist of
several openings close together, a few feet across and 2 or 3 feet in
depth, in the coarse pegmatite which caps the hill at this point.
The locality has been visited by George F. Kunz, of Xew York, and its minerals described by him.6 He describes the character and mode of occurrence of the topaz as follows:
This
locality is the first in New England that has furnished good, clear,
and distinct crystals of topaz, and thus far it has produced the best
crystals found in the United States. Of these crystals, nearly all the
finest were found in one pocket in clevelandite (lamellar albite) at
its junction with a vein of margarodite (hydromica) and one was
entirely surrounded by clevelandite. The finest crystals vary in size
from 10 millimeters to the largest, which measures transversely 60 by
65 millimeters and vertically 56 millimeters. They are transparent in
parts, and contain cavities of fluids, the nature of which has not yet
been determined. A few small perfect gems have been cut from the
fragments of a large crystal that was broken.
The
finest crystals are colorless or faintly tinted with green or blue.
Someopaque crystals are as much as 300 millimeters across the largest
part and weigh from 10 to 20 kilograms each. They are not perfect in
form, the faces are rough, and generally they were broken before they
were taken from the rock. The color in these rough crystals is more
decided than in the finer ones and is a light shade of either green,
yellow, or blue. The specific gravity of the transparent material is
3.54, and the hardness the same as that of the yellow topaz from Ouro
Preto (formerly Villa Rica), Brazil.
The properties of this topaz have been further discussed by Pen-field and Minor;c
its chemical composition has been studied and its alteration to
damourite has been described by Clarke and Diller." No topaz was
visible at the time of the writer's visit.
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