page_title: Guilford Quartz Monzonite
section_title: Early Quarrying
hierarchical_section_title: Guilford Quartz Monzonite / Early Quarrying
caption_attribution_description: English: Original caption: "Guilford and Waltersville Granite Company's Quarry, Guilford, MD."Guilford is now within the village of Kings Contrivance, Columbia, Maryland. The quarried rock is now called the Guilford Quartz Monzonite. Text from the volume referring to this figure: The horizontal joints, prominent in all the larger quarries, separate the granite into sheetlike masses, which usually have their strongest development near the surface, but in some quarries extend to the entire depth of working. Nowhere is this better shown among the Maryland granites than in the old Guilford and Waltersville Granite Company's quarry in the Woodstock area (Pls. IV, B; VI, B). The sheets may vary from a few inches in thickness at or near the surface to 2 to 10 feet at some distance below the surface. In the quarries on the Baltimore County side of Patapsco River, at Ellicott City, sheeting extends to the depth of working, more than 90 feet, and the sheets range, in thickness from 2 to 4 feet. In the quarries of the Woodstock area the sheets are from 2 to 6 feet thick, and in the quarries of the Guilford area from 3 to 10 feet thick. Approximately the same range in thickness is shown in the Port Deposit quarries, one of which has been worked to the extreme depth of 230 feet.
context_page_description: The Guilford Quartz Monzonite is a Silurian or Ordovician quartz monzonite pluton in Howard County, Maryland. It is described as a biotite-muscovite-quartz monzonite which occurs as discontinuous lenticular bodies which intrude mainly through the Wissahickon Formation.
  The extent of this intrusion was originally mapped in 1940 as the "Guilford granite". It was given its current name in 1964 by C. A. Hopson. Hopson grouped the Guilford Quartz Monzonite with the Ellicott City Granodiorite and the Woodstock Quartz Monzonite as "Late-kinematic intrusive masses."
context_section_description: The 1898 account of Edward B. Mathews of the Maryland Geological Survey of the quarry at Guilford (now within the town of Columbia) is as follows:
  The quarries at Guilford were originally opened about 1834, and were worked almost continuously from that date until the outbreak of the civil war in 1860. During the succeeding twenty-five years the operations were of little account, and little work was done until the Guilford and Waltersville Granite Company attempted to develop the industry in 1887. This effort lasted but a short time as all of the machinery was removed from the quarries in 1889. The industrial life of the district has been revived somewhat in recent years by the operations of Messrs. Matthew Gault and Sons, who commenced work in 1893, and by Messrs. Brunner and White, who opened a quarry of superior quality in March, 1895.
caption: Historical photo c. 1910 of the Guilford Quarry while in operation
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