Bluestone

Bluestone is the name given to several stones: (1) a feldspathic sandstone in the U.S., (2) a form of limestone native to the Shenandoah Valley in the U.S. (3) a form of dolerite which appears blue when wet or freshly broken in Britain, and (4) a basalt or olivine basalt in Australia.

In the United Kingdom

British bluestone known as Preseli Dolerite is an Igneous rock made up of Plagioclase Feldspar and Augite and is a Pyroxene mineral (calcium magnesium aluminosilicate. Ca, Mg, FE, AI, (Al,Si,206). It is medium grained dark and heavy rock, harder than granite. Preseli Bluestone tools, such as axes used to carve granite, have been discovered all over the British Isles. Many of them appear to have been made in or near Stonehenge, since there are petrographic similarities with the bluestones there.It is currently used to make jewelry and artefacts, mainly sold at the Stonehenge Visitors center and online.The bluestones at Stonehenge were placed there during the third phase of construction at Stonehenge around 2300 BC [cite web | last = | first = | authorlink = | authors = Jon Swaine | title =Stonehenge birthdate discovered by archaeologists | work = | publisher =The Telegraph (London) | date =2008-09-22 | url =http://www.telegraph.co.uk/news/3046095/Stonehenge-birthdate-discovered-by-archaeologists.html | format = | doi = | accessdate =2008-09-22 ] . It is assumed that there were about 80 of them originally, but this has never been proven since only 43 remain. The stones weigh between 2 and 4 tons each. They are believed to have been brought from the Preseli Hills, about 250 miles away in Wales, either through glaciation (erratic theory) or through humans organizing their transportation. If a glacier transported the stones, then it must have been the Irish Sea Glacier. Recently the archaeological find of the Boscombe Bowmen has been cited in support of the human transport theory, while new glacier modelling supports the erratic theory. Preseli Bluestone dolerite axe heads have been found around the Preseli Hills as well, indicating that there was a population who knew how to work with the stones (see N P Figgis Prehistoric Preseli). There is also a legend of Merlin having miraculously transported the stones himself. There are many problems as to the provenance of the Bluestones to be resolved.It is hoped that recent excavations at Stonehenge should bring new insights to the Bluestone mystery.A summary (in graphic form which outlines the major aspects of the Stonehenge "bluestone conundrum has recently been published by Anthony Johnson(Thames and Hudson 2008)" Solving Stonehenge: The New Key to an Ancient Enigma" (fig.89.P165.) ISBN 978-0-500-05155-9

In the United States

The best known American variety of bluestone is a feldspathic sandstone, which is produced in hundreds of small quarries in adjacent areas of Pennsylvania and New York. The Pennsylvania Bluestone Association has 105 members, the vast majority of them quarriers. The other, lesser known, type of American bluestone is formed from a different sedimentary rock, limestone. The limestone is abundant in the Shenandoah Valley of Virginia yet The Frazier Quarry is the only remaining quarry that cuts dimension stone from it.

Bluestone from Pennsylvania and New York is commercially known as bluestone or Pennsylvania Bluestone. These are a group of sandstones defined as feldspathic greywacke. The sand-sized grains from which bluestone is constituted were deposited in the "Catskill Delta" during the Middle to Upper Devonian Period of the Paleozoic Era, approximately 370 to 345 million years ago. If the initial deposit was made under slow moving water the ripples of the water action on the sand or mud will be revealed. This deposition process may be seen today at any ocean beach in shallow water or in a stream bed where conditions allow it to be observed. The term "bluestone" is derived from a deep-blue-colored sandstone first found in Ulster County, New York.

The Catskill Delta was created from run off from the Acadian Mountains ("Ancestral Appalachians") which covered the area where New York City now exists. This Delta ran in a narrow band from southwest to northeast and today provides the base material for the high-quality bluestone which is quarried from the Catskill Mountains (and Northeast Pennsylvania).

As the product became more popular as an architectural and building stone and demand grew, quarrying for it spread throughout south central New York and northeast Pennsylvania. It is a unique commodity of particular value to the economy of Susquehanna County, Pennsylvania.

Bluestone from the Shenandoah Valley is regionally known as bluestone but a less ambiguous name is Shenandoah Valley Bluestone. The limestone formed during the Ordovician Period approximately 450 to 500 million years ago, but it was formed at the bottom of a relatively shallow ocean that then covered what is today Rockingham County, Virginia. However, the limestone that accumulated in Rockingham County was darker in color than most other limestone deposits because it was in deeper waters exposed to less light. The darker blue color resulted in limestone from this region to be dubbed bluestone and with two sequences measuring about 10,000 ft, it gives the area one of the largest limestone deposits in the world. The stone eventually fades from a deep blue to a light grey after prolonged exposure to the sun.

Given the abundance of the stone in the Rockingham County area, the first settlers used it as foundations and chimneys for their houses. When James Madison University was built, the native bluestone was used to construct the buildings because of its high quality and cultural ties ( Washington and Lee University and Virginia Military Institute are also largely constructed from this stone), and JMU refers to a major portion of their school as the "bluestone" campus.

In Australia

Australian bluestone is a basalt or olivine basalt, and is quarried by one full-time producer and one part-time producer.

In Victoria, Australia, bluestone was one of the favoured building materials of the 1850s during the Victorian Gold Rush.

In Melbourne it was extracted from a quarry in the Clifton Hill area and used extensively in the 19th century. Because the material was difficult to carve, it was predominantly used for warehouses and the foundations of public buildings. Significant bluestone buildings include the Melbourne Gaol, HM Prison Pentridge, St Patrick's Cathedral, Victoria Barracks, Melbourne Grammar School, Deaf Children Australia and Victorian College for the Deaf, Royal Victorian College for the Blind, the Goldsborough Mort warehouses (Bourke Street) and Timeball Tower. It was also used extensively for cobblestone roads, many which still exist in some of Melbourne's smaller lanes as well as walls, bridges, curbs and gutters in many of the inner suburbs. Some examples of structures that use the material include Princes Bridge and Federation Wharf and Hawthorn Bridge. Because of its distinctive qualities, post-modern Melbourne buildings have also made use of nostalgic bluestone, including the Southgate complex and promenade in Southbank, Victoria and apartments such as the "Melburnian".

It was also sourced in many other regions of the Victorian volcanic plains and used in towns and cities of central and western regions including Ballarat, Geelong, Port Fairy and Portland.

References

Center for American Places, Inc. Santa Fe, NM. 2004.

External links

* [http://www.brianjohn.f2s.com/bluestonesimp58.html Examination of the conflicting theories relating to the Stonehenge bluestones]
* [http://www.netcomuk.co.uk/~brianj/bluestones59.html Enigma of the Stonehenge Bluestones and the Preseli Hills]
* [http://www.wessexarch.co.uk/projects/wiltshire/boscombe/bowmen/stonehenge_bluestones.html Wessex Archaeology's Bluestone information]
* [http://fieldstone2001.tripod.com/bluestone.html How American bluestone is quarried]
* [http://www.susqco.com/subsites/ecodev/pages/bluestone.htm Pennsylvanian bluestone]
* [http://www.tuin-steen.nl/sierbestrating/terrastegels/blue/index.php AGI Trade Solutions in naturalstone]
* [http://www.darderstoneworks.com/articles.htm Article on Cultured Bluestone]
* [http://www.frazierquarry.com/v.php?pg=23 History of Shenandoah Valley Bluestone]
* [http://www.britannia.com/history/preseli_blue.html Secrets of the Preseli Bluestones]
* [http://www.stonehengestones.com Preseli Bluestone Jewelry]
* [http://www.nielsen-inc.com/inside/insidenielsen/Spring2007.pdf Inside Nielson Magazine]
* [http://csmres.jmu.edu/geollab/vageol/outreach/fieldtrips/rockingham/whole.html A Brief Geologic History of Rockingham County]
* [http://news.bbc.co.uk/2/hi/science/nature/7625145.stm Dig Pinpoints Stonehenge Origins]