Vermont Slate

Vermont slate is natural roofing slate quarried in the Slate Valley, a district straddling the border between western Vermont and eastern New York State, centred on Granville, New York. It is known for its range of natural colours.

Colours

Slate Valley is one of the few places in the world that produces coloured slate in commercial quantities. Colours include green, grey, black and red, which allows patterned roofs to be laid using slates of contrasting colour.

History

Slate was quarried at Fair Haven, Vermont, by 1839. Immigrants from north Wales brought quarrying skills and drove a production boom that peaked in the second half of the 19th century. In 2003 the district had 23 full-time mines employing 348 people.

Other American slate districts

• Pennsylvania: the first commercial slate quarry in the United States opened in 1785 in Peach Bottom Township. The Lehigh and Northampton county area, around Slatington and Bangor, has roughly 400 former quarries and in 1929 produced nearly half of the value of US slate output.
• Maine: slate from the Monson district roofs St Patrick's Cathedral in New York City.
• Virginia also produces slate.

Standards

In the United States, roofing slate is specified to ASTM C406, which grades slate S1, S2 or S3. S1 slate is rated for a service life of more than 75 years. US quarries mostly produce slate about 1/4 to 3/8 in (6-10 mm) thick, and the industry redefined "standard" slate in 2015 as nominal 1/4 in (6 mm).