Main Quarry Operations

The USGS (Watson -1910 Granite of the Southeastern United States - see below) provided a detailed description of the Guilford quarries and is repeated below for ease of reading:

GUILFORD AREA.  GENERAL STATEMENT.

The Guilford granite area, located in Howard County, a few miles southwest of the Ellicott City area, is of large size and irregular outline, as shown on the map (PL I). It is bordered on the north and west by the Baltimore gneiss and on the east by the gabbro. It is also covered in part by the gravels and clays of the Coastal Plain. The granite from this area differs from that of the other areas in the State in containing both light mica (muscovite) and dark mica (biotite). Muscovite occurs as a subordinate constituent in some of the other Maryland granites, but not so abundantly nor characteristically as in the granite of this area.

The granite of the Guilford area varies from a coarse-grained granite of red color at the Guilford Granite and Stone Company's quarry through a medium-grained reddish-gray granite at the Penny quarry to a fine-grained medium-gray granite at the Maryland Granite Company's quarry. This last-named type is the one most extensively quarried, because it possesses durable qualities that give it a wide range of uses.

 The quarries are located on Little Patuxent River about 5 miles northwest of Annapolis Junction and about 2 miles from the nearest railroad point Savage Factory. They were opened about 1834 and were worked almost continuously until the/outbreak of the civil war in 1860. Very little work was done from 1860 to 1893, but in 1893 the quarrying industry was revived and has continued to the present time.

DESCRIPTIONS OF QUARRIES.

Four quarries, located close together on Little Patuxent River, have been opened. These are, in order of importance, the Maryland Granite Company's quarry, Guilford and Waltersville Company's quarry, Penny quarry, and Guilford Granite and Stone Company's quarry [webmaster's note - the last quarry was operated by the Howard Granite Company starting 1902].

Maryland Granite Company

The Maryland Granite Company's quarry is on the east side of Little Patuxent River 2 miles north of Savage Factory and about 5 miles northwest of Annapolis Junction. It is the principal quarry in the Guilford area and was the only one operating at the time of examination in 1908. The rock is a muscovite-biotite granite of medium-gray color and of even, fine grain, with biotite uniformly disseminated and in excess of muscovite. It consists of potash feldspar (orthoclase and microcline), soda-lime feldspar (oligoclase), quartz, biotite, and muscovite, together with accessory zircon and apatite and secondary chlorite, epidote, muscovite, and kaolinite. Intergrowths of feldspar and quartz are numerous. The larger feldspar grains show enclosures of feldspar and quartz. The stone takes a fine polish, the durability of which is favored by the smallness of the biotite scales.0 A chemical analysis of this granite is given in column 3 of the table on page 42. The percentages of soda and potash show that the rock contains nearly equal amounts of the potash and soda-lime feldspars.

The quarry measures about 500 by 300 feet and has a depth of about 100 feet. The average depth of stripping is about 10 feet.  The sheets, 3 to 10 feet thick, are approximately horizontal and tapering lenticular. Vertical joints strike north-south and eastwest, recurring at wide intervals. Many of the joint surfaces are slickensided, indicating movement in the granite mass. There are a few dark basic segregations (knots), the largest observed not exceeding 6 inches long by 3 inches wide. No pegmatite dikes were noted.

The product is used chiefly for monuments, though much of it is used for general building purposes in the dressed and rough states, largely in the rough. Much of the coarse waste is worked into paving blocks. Very little of the stone is used for curbing and no crushed stone is produced. The principal markets are in Maryland and Pennsylvania. Shipments have been made as far west as St. Louis and Chicago, north to New York, and South to Atlanta.

Guilford and Waltersville Granite Company

The Guilford and Waltersville Granite Company's quarry is on the east side of Little Patuxent River a short distance from the Maryland Granite Company's quarry. Work had been suspended sometime prior to the writer's examination in 1908. The rock is a muscovite-biotite granite of medium^gray color and of even, fine grain, with biotite uniformly disseminated and in excess of muscovite. This granite appears to be identical in composition, color, and texture with that of the Maryland Granite Company's quarry, and is equally well adapted to the same uses.

Penny Quarry

The Penny quarry is on the north side of Little Patuxent River about 300 feet northeast of the Maryland Granite Company's quarry. The quarry was nearly filled with water at the time of the writer's examination in 1908, but during its activity it was operated by the Maryland Granite Company.  

The quarry is a small one, less than 100 feet square and less than 50 feet deep. The granite is a biotite-muscovite granite of medium pinkish-gray color and medium-coarse grain. Its feldspar contrasts strongly in color with that of the Maryland Granite Company's granite in having a pronounced pinkish cast. The rock is also of coarser texture and differs in composition, muscovite being in excess of biotite. It consists of potash feldspar (orthoclase and a See Maryland Geol. Survey, vol. 2,1898, PI. XVI, for reproduction of a polished surface of a block of this granite microcline), soda-lime feldspar (oligoclase), quartz, muscovite, and biotite, together with accessory apatite, and zircon and secondary chlorite. Microcline and orthoclase are present in nearly equal proportion; the latter is intergrown with a second feldspar as microperthite.

The feldspar shows very general alteration. The larger feldspar individuals inclose rounded grains of other feldspar and quartz. Intergrowths of feldspar and quartz are observed. Vertical joints strike north-south and east-west. Many of their surfaces show slickensides. Segregations (knots) and pegmatite dikes were not observed in the granite.

The Guilford Granite and Stone Company [note: it is the Howard Granite Company]

The Guilford Granite and Stone Company's quarry is on the opposite (west) side of Little Patuxent River from the Maryland Granite Company's quarry. It comprises three small openings, the largest one of which is about 75 by 60 feet and 50 feet deep. The object of the company was to produce crushed stone, and a large crusher was erected and operated near the quarry. Operations were suspended about four months prior to the writer's examination in March, 1908.

The rock is a biotite-bearing muscovite granite of pronounced reddish color and coarse grain. The feldspar which imparts the red color to the granite contrasts strongly with the dark glassy quartz.  The granite of this quarry is similar in composition to that of the three other quarries in the Guilford area described above, except that muscovite is the principal mica and is greatly in excess of the biotite. The rock consists of potash feldspar (orthoclase and microcline), soda-lime feldspar (oligoclase), quartz, muscovite, and very little biotite, together with accessory apatite and zircon. Potash feldspar is in excess of soda-lime feldspar, and both are considerably altered. Orthoclase is intergrown with a second feldspar as microperthite. Intergrowths of feldspar and quartz occur.

The granite differs from the other granites quarried in the Guilford area in being coarser grained and of a more pronounced red color and in having a larger preponderance of muscovite over biotite. Closely spaced vertical joints are prominently developed. There are several sets, intersecting at approximately right angles and recurring at such short intervals as to render the quarrying of dimension stone very doubtful.

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