222 PHYSIOGRAPHY, GEOLOGY AND MINERAL RESOURCES

obtained from this area, but the gold is so unevenly distributed that
it has not yet been worked with profit. Reports are frequent of the
discovery of gold in other portions of Maryland, but these finds are
generally without foundation and none have as yet been proved to
be of any value. At the time of the last census in 1890 the amount
of gold produced in Maryland was valued at $16, 885. Practically
nothing is now being done in the development of the gold properties.

THE MINERAL PAINTS.

Mineral paint has been produced at several points in Maryland
and in widely different geological horizons. Large quantities have
been obtained in the past from the brown iron ore deposits in Fred-
erick county, but nothing is being done at the present time in that
region. Ochre mines have also been operated in Carroll and Howard
counties, and something is being done in these regions at the present
time.

Important deposits of paint ore have also been obtained from the
Patapsco formation in Anne Arundel and Prince George's counties.
This ore occurs in a fine and highly ferruginous clay and can be
worked readily. There are several industries at the present time
established in this belt and the opportunities for its further develop-
ment are exceedingly good.

The value of the mineral paints produced in Maryland during 1896
aggregates $2, 000.

THE DIATOMACEOUS EARTH.

Diatomaceous earth, known to the trade as Infusorial earth, or
Tripoli, has been produced in larger quantities in Maryland than
elsewhere in the United States. The Diatomaceous earth in Mary-
land is found at the base of the Chesapeake formation and consists
of deposits, which in northern Calvert and Charles counties attain a
thickness of 30 to 40 feet; the most extensively worked localities are
situated near the mouth of Lyon's creek on the Patuxent river and at
Pope's creek on the Potomac river.

Diatomaceous earth is made up of the microscopic shells of diatoms.