Geologic History of the Ideal Building Material: From 245 million to 208 million years ago during the Triassic geological period, vast beds of rock were being formed. Near the end of this period, the only Triassic formation of Eastern North America was deposited in downfaulted troughs, parallel to the Appalachians, from Nova Scotia to North Carolina. Where oceans and waters had been, upheaval created marshes and ferns where dinosaurs roamed and cycads grew. Sand and silt collected in huge basins and time, with the assistance of pressure, began the relentless work of compressing these grains into rock. Triassic Brownstone, rarely found in the Earth’s surface crust, is a product of this time.
Composition and uses: As a variety of sandstone, brownstone is one of the strongest and yet easily carved building materials, composed from consolidated sand bound together by an interstitial cement of iron oxide. It is this iron oxide which gives brownstone its characteristic color; however, when inclusions of other elements such as feldspar, aluminum, magnesium, etc. occur in the stone it can have a gray, blue, pink or purple hue.
This stone is commonly called freestone because it can be worked freely in every direction, a characteristic that made it popular with stone cutters and masons.
Strength and durability of Hummelstown Brownstone: Experiments made with the government testing machine at Watertown, Massachusetts in 1882 and 1883 calculated the tons/sq. in. crushing load of various stones. Montgomery County blue marble was 700, Indiana limestone was 500, 840 for Hummelstown brownstone, and 260-1,000 for Ohio yellow sandstone. George P. Merrill, in his classic study Stones For Building and Decorating, reported that in 1875, the Q. A. Gilmore Company found the crushing strength of the stone to be 12,810 to 13,600 lbs./sq. in. which was similar to that quarried by its competitors in Portland,
Connecticut, as well as Medina and Albion, New York. This far outstripped the crushing capacity of the stone quarried at Beria, Ohio, and East Longmeadow, Massachusetts, two other competitors in the brownstone business.
In 1912 Heinrich Ries in his book Building Stones and Clay Products listed the crushing strength of Hummelstown brownstone at 14,750 lbs./sq. in. which exceeded nearly all other companies on the list.
The steps at the front of the First Lutheran Church in Carlisle, PA are a fine example of the durability of the brownstone, for the edges of each step, despite almost a century of wear, appear to be as sharp as the day they were set in place.
February 25, 1878
We have the great pleasure of presenting to you a certificate signed
by the Architects and Builders of Philadelphia which bears testimony of the
quality and durability of the Stone from the Quarries of the Pennsylvania
Brown Free Stone Company known as Hummelstown Brown Stone which
are most favorably known and used in this market. The undersigned
Architects and Master Stone Cutters and Builders of the city of
Philadelphia do hereby certify that Hummelstown Brown Stone from the
quarries of the Pennsylvania Brown Free Stone Company in Dauphin
County, Pennsylvania is one of the best and most durable Brown Stones or
Sand Stones Known in this country.
signed, Architects Collins and Autenrieth, Furness, Hutton, Packer, Hewitt, Muller, Killen, Dougherty et al.
–from Letter of Architects to Commissioners in charge of building Pennsylvania State Hospital,” February 28, 1878, Hummelstown Brownstone Manuscript Group, Dauphin County Historical Society.
Note: The bias of Muller and Killen, Philip Dougherty, and William Armstrong is understandable in that they were minor stockholders in the company. Nevertheless, the signatures of some of Philadelphia’s top-flight architects who had no financial investment in the company speaks well for the product. Frank Furness trimmed his tour de force, the Pennsylvania Academy of Fine Art, with the stone; Addison Hutton used it for trim on the administration building of the State Hospital in Harrisburg as well as various buildings for Asa Packer at Lehigh University; George Hewitt clad his Philadelphia Bourse with it, and Collins and Autenrieth used it for revisions to the Library Company of Philadelphia.
Information on this page gratefully excerpted from “A study of the Hummelstown brownstone industry and its contribution to the American building arts”, by Ben F. Olena
Full text accessed April 2012: http://quarriesandbeyond.org/articles_and_books/hummelstown/hummelstone_brownstone_page.html
United States Geological Survey, “Bulletin 840,” 1933, pp. 72 – 73.
“Hummelstown Brownstone,” (New York: Frank A. Lent Publisher, 1907), p. 403, Hummelstown Brownstone Manuscript Group, Hummelstown Area Historical Society. 22