The Not-so-blue Stone

By Cory Sekine-Pettite

Bluestone — a variety of sandstone — is a beautiful and versatile building material, so-named because the stone appears blue when wet or freshly broken. The name is a bit of a misnomer, however, because the stone can be found in a range of colors. Geologically, bluestone is a fine-grained arkosic sandstone, also geologically referred to as a feldspathic sandstone. Though it is a durable stone that resists cracking, bluestone is highly prized as a building material because it can be easily separated into slabs of nearly any desired size. The stone usually is split and used in outdoor paving, such as walkways and patios.

More Info Quarry Locations: North America: New York and Pennsylvania Europe: United Kingdom Australia Applications: Architectural accessories Interior accessories Building stone Countertops Fireplaces Flooring Landscaping Sculpture and carving Appropriate Finishes: Cleft Flamed Honed Natural Polished Sandblasted Sawn (rough) Split face Tumbled

The upper levels of bluestone deposits are well stratified and can be separated into slabs easily. Sawn from the quarry using concrete saws, blocks of the stratified stone are set on edge to dry in the sun. This drying process exposes the natural seams in the stone, which is then split into pattern bluestone. Bluestone tile also can be cut from this horizontally bedded upper layer. Below the beds, the stone develops a more solid structure. At this level, big blocks can be removed by plug and feather. Cubes of the stone, which can weigh from five to 10 tons, are fabricated into slabs in a similar fashion as granite.

Quarries
Tough and weather-resistant, bluestone is easy to use, and is available in both dimensional and irregular sizes of varying thicknesses. It is often quarried as well-laminated, horizontally bedded sandstone, and that is one of its key traits. One of the flattest of all natural stones, Bluestone's tight dimensional tolerances work especially well in many outdoor environments, but it is well suited for indoor applications as well.

Largely known as a North American stone, bluestone is found mostly in the Catskill Mountain region of New York and in northeast Pennsylvania where the term "bluestone" was first applied to a deep-blue-colored sandstone found in Ulster County, Pa. The geography (and geology) of this region was created from runoff from the Acadian Mountains ("Ancestral Appalachians"), which covered the area now known as New York City. This "Catskill Delta" ran in a narrow band from southwest to northeast and today provides the base material for the high-quality bluestone that is quarried from the two states. Bluestones from this source often are called Pennsylvania River Rock or variations of this name, depending on the market or origin of the stone.

Outside the United States, bluestone varieties can be found in the United Kingdom and Australia, where the building material seems to be increasing in popularity for new construction as well as reconstruction. In Melbourne, Australia, for example, bluestone was used to build many historic buildings, such as HM Prison Pentridge in the 19th century, and is used today to construct walls, bridges, curbs and gutters.

Colors
Bluestone is a great way to help a client bring the bountiful colors of the outdoors into or around their home or place of business. The material's color range is among the most diverse in nature, consisting of assorted pastel shades of steel blues; tropical greens; regal shades of lavenders and purples; golden yellows; as well as more sophisticated shades of gray, and lighter hues of beige, brown and rusty variations. Each stone is unique in its pigmentation, making a subtle change from stone to stone when set in paving or other applications. The result can provide an almost jewel-like effect that is both whimsical and sophisticated. This subtle, but striking, aesthetic effect makes bluestone a coveted building stone.

Applications
The durable texture of bluestone makes it ideal for almost any application. The material is sold as both dimensional and flagstone, providing opportunities for use as paving, pool coping, wall veneer, countertops, patios, architectural facings, fireplaces, sills, and as a basic building material for churches, institutions, homes and businesses. Bluestone is available in many formats and sizes such as irregular slabs, tumbled pavers, wall rock and tumbled gravel.

Further, the versatile stone offers near-endless possibilities when it comes to finishes, whether you desire cleft, flamed, sawn, split-face or tumbled finishes. Bluestone also can be treated thermally, sanded and rubbed, or honed; honed bluestone is said to be a superb material for countertops. Basically, for whatever application you can imagine, it can be carved or cut from bluestone.

Interesting Facts
The famous rocks of Stonehenge are bluestone. According to historians, the stones were placed there during the third phase of construction at Stonehenge around 2,600 B.C. The stones weigh approximately four tons each. They are believed to have been brought from the Preseli Hills, located 250 miles away in Wales, either through glaciation (erratic theory) or through humans organizing their transportation; scientists are still debating these theories.

In the United States, one of the most well known structures built from bluestone — and perhaps the oldest bluestone structures in this country — is the Starrucca Viaduct in Lanesboro, Pa. The viaduct is 1,000 feet long with 17 arches rising between 90 and 100 feet high to support the span. Completed by the Erie Railroad in 1848, the viaduct is now a National Civil Engineering Landmark. Quarrying became a local industry after the viaduct was built, and in the mid-1800's at least six quarries near the viaduct were cutting bluestone, using the railroad to ship the material across the Northeast. The Starrucca Viaduct is still used by the Norfolk-Southern Railroad.

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