210 PHYSIOGRAPHY, GEOLOGY AND MINERAL RESOURCES

The fine-grained, compact and variegated marbles of the western
portion of the Piedmont Plateau compare favorably in their quality,
texture and beautiful veining with well-known marbles from Vermont
and Tennessee, and are deserving of much more attention than they
have heretofore received. These highly colored and variegated mar-
bles are found chiefly in Carroll and Frederick counties. In the
Wakefield valley, west of Westminster, a beautifully mottled red and
white marble occurs; others with a black and white, gray and white
or blue and white veining occur near New Windsor and Union
Bridge, and still others of a warm yellow with lighter veining have
been derived from the same area. These marbles have had little
economic significance hitherto on account of the limited extent of the
deposits, but are well adapted for purposes of interior decoration.

The blue limestones of the Appalachian district have been used to
some extent for building purposes, more especially in Hagerstown,
where several churches have been constructed of this material. This
blue limestone changes its color rapidly on weathering, but has a
pleasing effect. A quarry of very compact, even-grained and pure
cream white marble has been opened just beyond Edgemont Station
in Washington county on the eastern edge of the Hagerstown valley,
but as yet has not been much developed.

Another stone which may be classed as a limestone,, on account of
the high percentage of lime which it contains, is the conglomerate or
breccia of Triassic age found in the Frederick valley. It is known as
" Potomac marble " or " calico rock, " and has received noteworthy
application as a decorative stone in the old Hall of Representatives
at Washington, where it forms a series of beautiful columns. It
occurs well exposed at Washington Junction, Frederick county, and
extends northward along the base of the Catoctin Mountain. It
consists of large and small angular and sub-angular fragments, mostly
of the valley limestone, although many other rocks like quartz, slate,
granite, porphyry, etc., also occur imbedded in the red ferruginous
cement. When polished it presents a very beautiful appearance.

The total value of the marble and limestone employed as structural
materials in 1896 was $110, 500.