Formed about 500 million years ago in the Paleozoic Era, slate rock is an example of nature's ability to produce materials with properties that outperform many man-made substitutes. One of the earliest identified examples of slate rock as a writing medium, the Palette of Narmer, dates from 3000 B.C. and records the triumphs of the Egyptian King Narmer. Since that time, scholars, tradespeople, builders and artists have used slate in pursuit of many diverse crafts.
Slate rock splits easily into strong, thin sheets and has many diverse uses. Slabs of slate, when sawn to specified dimensions, produce regular blocks that make durable roof tiles, floor tiles, flagstones and structural building components. Slate also contributes widely to preserving human knowledge of the past. Carved slate gravestones in historic cemeteries throughout the United Kingdom honour the memory of distinguished individuals who might otherwise have gone to the grave unknown. In the modern day, precision-ground slate slabs, accurate to hundredths of a millimetre, form the playing bed of every tournament-grade snooker table.
Durability and weight
The hard-wearing nature of slate rock ensures longevity, and many slate-roofed houses built in the late 18th century still stand as examples of slate's superior weather-resistant properties. The cost of the skilled labour and the solid load-bearing structure needed for a heavy slate roof eventually contributed to the decline of the industry, as modern roofing materials were lighter, cheaper and easier to install. Even when the less durable modern roofs needed replacement, the flimsier construction of newer houses left them unable to bear the weight of slate tiles.
Depending on the exact chemical composition of the rock during its formation, slate occurs in many colours other than the familiar grey, including green, red, black and purple. Consequently, slate is a popular gem-rock, often carved and engraved to form decorative artefacts including beads, jewellery and ornaments. Coloured roofing tiles provide builders with options for individual touches to designer properties. The original blackboards owed their name to colour of the slate used to make them, and slate has thus contributed to the early education of generations who might otherwise have had no opportunity to learn to write.
Coefficient of friction
When rubbed with a wooden or metal object, slate produces a range of sounds that result from the friction between the two surfaces. This feature of slate's behaviour provides a practical way for a hunter to imitate the sound of his prey, and a variety of friction calls are popular with those who hunt turkey, duck and other game birds. Decorative antique calls are sought-after collector's items, often worth over a thousand pounds.
- The University of Vermont: A study in slate
- Minnesota State University: The history of ancient Egypt: Menes
- U.S. Geological Survey: 2006 Minerals yearbook: Stone, dimension
- Billiard Congress of America: BCA equipment specifications
- Pennsylvania State University Libraries: In pursuit of the quarry: Pennsylvania's slate belt
- Central Michigan University: Gemrocks: Ornamental and curio stones: Slate