associated
with a great many worthless pebbles, such as black and red jasper,
quartzite, white milky quartz or chalcedony, and waxy gray chalcedony.
A quantity of the waxy chalcedony is found in place and loose on the
surface between the Mcintosh ranch and Lankin Pass.
The
agates range from opaque white and gray to highly translucent gray with
black, dark brown, reddish to yellowish-brown dendritic markings. Those
with the black and dark-brown markings are most common. The dendrites
consist of tufts or patches of oxides of manganese and iron. They show
great variations in size and in delicacy of pattern. Some are small
rounded tufts too dense to show individual lines, and others are as
much as 2 or 3 millimeters across, exhibiting very delicate, mosslike
or seaweed-like markings. The black dendrites furnish the prettiest
gems. Groupings of the dendrites in such manner as to show complex
landscapes, as in the Montana moss agate, apparently do not occur, and
the gems depend on the perfection of the individual dendrites for.
their beauty.
The
agate beds have not been exploited commercially to the present time.
Most of the specimens have been collected by occasional visitors who
have not placed the stones in the regular gem market.
AMETHYST. PENNSYLVANIA.
The
occurrence of amethyst at many localities in Chester and Delaware
counties, in southeastern Pennsylvania, have been mentioned by Kunz x and Dana.2
The localities given include, in Chester County, several places in east
Bradford, Pocopson, Birmingham, and Newlin townships; and in Delaware
County, Aston, Birmingham, Chester, upper Chichester, Concord,
Edgemont, Marple, Middletown, upper Providence, and lower Providence
townships. Most of these discoveries were made before 1890, and since
that time only occasional amethysts have been found. The majority of
the amethysts have not been of fine quality, but a few specimens of
fine crystals capable of yielding beautiful gems have been obtained.
At
present very few persons in the region take an interest in these
minerals or know of the localities, and since much of the land has
grown up in brush or been turned into meadow, there are few
opportunities for the further discovery of amethyst. An examination
was made of one of the old localities near Village Green, in Aston
township, now owned by G. L. Mills. Some pits in a field on this place
where good amethyst was obtained, are now filled up. A careful search
on the ground near the pits yielded only a few colorless quartz
crystals. No rock crops out around these amethyst pits, but the area is
mapped as Wissahickon gneiss by F. Bascom.3
Mr.
John H. Smedley, of Media, who was formerly much interested in the
minerals of this region, knows the location of many of the amethyst
deposits. He states that few finds of value are now made and that under
the present conditions much prospecting and digging will be necessary
to uncover gem material at many of the places.
1 Kunz, G. F., Gems and precious stones, pp. 112-115, Scientific Publishing Co., New York, 1890. * Dana,
J. D., System of mineralogy, 6th ed., pp. 1067-1088, 1909. a U. S.
Geol. Survey Geol. Atlas, Philadelphia folio (No. 162), 1909.
