Maryland
Geological Survey, Volume 1, 1897
The
manufacture of fire-brick has been one of the characteristic industries of Maryland for 50
years, and the brick made from the fire-clays of the Pottsville formation in Allegany
county are regarded as the best in this country. The oldest fire-brick concern in Allegany
County, that at Mount Savage, was organized in 1841 and was the first of its kind in the
United States. The main fire-clay deposit lies near the bottom of the coal measures and
the clay bed ranges from 5 to 20 feet in thickness. It is divided into two varieties,
designated as the hard and soft clay. The hard clay is of a gray color, shading almost to
black; it is non-plastic, unless ground into an impalpable powder, and disintegrates but
little upon exposure to the weather. The soft clay is very plastic, much lighter in color
and crumbles rapidly under atmospheric influences. The impurities in this clay are fewer
and smaller in amount than in most other fire clays. The two most valuable characteristics
of this clay are its freedom from potash and the large proportion of silica to alumina.
The clay industry has grown rapidly in importance during recent years, and the value of
the output during 1896 was $1, 753, 003.
Maryland State Archives
Volume 423, Page 215