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|A Geologic Walking Tour of Building Stones of Downtown Baltimore, Maryland||contact: Dale Shelton (firstname.lastname@example.org)|
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STOP 4: 120 EAST REDWOOD STREET BUILDING
From the corner of Light and Redwood Streets walk east to the building at 120 East Redwood Street, Stop 4 (currently the location of Metropolitan Health and Fitness). The stone on the exterior of the building is a fine-grained granite. The smaller crystals indicate a faster cooling rate than in the other granites observed previously. This granite has two contrasting finishes: a smoother finish from a multiple point chisel and a rougher finish from a single point chisel (these finishes are referred to in the building-stone trade as a flat 6 or 8 cut bush hammered finish and a rough point finish with a margin draft, respectively) (Figure 4a).
Notice that along the base of the vertical rock panels below the window sills, the stone is spalling, or peeling away (see also Figure 4a). This may be due to physical disintegration by frost action, in which water in fractures in the rock freezes, expands, and wedges the rock apart, or to chemical decomposition in which the minerals in the rock react with atmospheric oxygen and moisture to alter the composition of the rock. Both of these processes may actually be taking place simultaneously; collectively they are termed weathering.
Metropolitan Health & Fitness
120 E Redwood St
Baltimore, MD 21202
4: Fine-grained granite showing two contrasting
finishes: a smoother bush hammered finish (left)
and a rough point finish (right); weathering
of granite also shown at the corner of the smoother block (Stop 4).
This pamphlet was prepared by
Sherry McCann-Murray, with contributions and photography by the Environmental
Geology and Mineral Resources Program of the Maryland Geological Survey.
Adapted for the Internet from Educational Series No. 10. For more information see Building Stones of Maryland .
Compiled by the Maryland Geological Survey, 2300 St. Paul Street, Baltimore, MD 21218
This electronic version of "A Brief Description of the Geology of Maryland " was prepared by Bob Conkwright, Division of Coastal and Estuarine Geology, Maryland Geological Survey. Please send comments on this page to Dale Shelton (email@example.com)
State of Maryland
Department of Natural Resources, Resource Assessment Service