MARYLAND GEOLOGICAL SURVEY 227

LEAD AND ZINC. —Traces of galena and zincblende were early noted
near the quarries at Jones' Falls in Baltimore county, but much more
decided indications of these minerals occur in connection with the
crystalline limestone in the western part of Carroll and the eastern
part of Frederick counties, where attempts have been made to mine
them in the region to the southwest of Union Bridge. In spite, how-
ever, of the frequent traces of both these minerals throughout central
Maryland, it may be confidently asserted that neither will probably
be found to occur in amounts that will repay mining.

MANGANESE, ANTIMONY, MOLYBDENUM. —The traces of these metals
which have been detected in Maryland are even more insignificant
than those of lead and zinc. Manganese was once mined a short
distance west of Brookville in Montgomery county, but the deposit
was not sufficiently extensive to be profitable. More recently man-
ganese has been reported from Allegany county. Specimens of the
sulphide of antimony have been obtained in the Middletown valley,
but nothing is known of its occurrence or extent. The earliest dis-
covery of molybdenite mentioned on this continent was made at the
Jones' Falls gneiss quarries in 1811, but the deposit is not sufficient
to be of economic value.

SOAPSTONE. —Soapstone is a compact variety of talc and in com-
position is a hydrous silicate of magnesium. It has been worked to
some extent in Carroll, Harford and Montgomery counties, the most
extensive deposits being found a short distance to the northwest of
Marriottsville in Carroll county, where for a time the stone was sawed
into slabs for the manufacture of bath tubs. In later years the pro-
duct has been ground and sold to manufacturers of fire-proof and
acid-proof paints, although some slabs are sawed out occasionally for
fire-brick and hearthstones.

ASBESTOS. —The crystalline rocks of Maryland contain several
deposits of asbestos, most of which, however, is not true asbestos,
although it passes under that name, but is the fibrous variety of ser-
pentine known as chrysotile. These deposits are in both quality and
quantity of production inferior and unimportant. In 1880 one mine
in Harford county and three in Baltimore county produced a total