Roofing slates of the world, part I
04/07/2013 2 Comments
Images of hand specimens and thin sections of slates from several world´s locations. Real color of the specimens may vary with respect of shown in the images.
1 – Slate from Labassere, Pyrenees, France. Dark and homogeneous slate quarried in the French Pyrenees. Nowadays, the quarry keeps a small production focused in the local market. Stratigraphy: Ordovician. Sample picked directly at the quarry.
2 – Shale from Minas Gerais, Brazil. Green rock, although other colors are quarried. It has a metamorphic grade slightly lower than slate. Also, it may have carbonate inclusions (red colored zones in the 200 zoom microphotograph) located in sandy levels. Stratigraphy: Bambui group, Ediacaran. Sample courtesy of Pizarras SAMACA.
3 – Red slate from Newfoundland, Canada (Trinity slate). Fine-grained and homogeneous slate with abundant iron oxides which gives it the red color. Stratigraphy: Bonavista Formation, Lower Cambrian. Sample courtesy of Laboratorio del Centro Tecnológico de la Pizarra.
4 –Himalaya slate. This rock is actually a layered volcanic rock, as it can be deduced due to the epidote crystals seen in the thin section. There are some studies about roofing slates in the Nepal and Himalaya zone Himalaya (Neupane 2007, Neupane 2012). The production potential for this area is still unknown. Stratigraphy: Nourpul and Benighat Formations, Neoproterozoic/Lower Cambrian.
5 – Shale from Jiangxi, China. Light grey rock, fine grained, with homogeneous texture and abundant opaque minerals. Roofing slates form China are very varied both from petrological and commercial points of view. Thus, there are some exceptional god materials together with other with less quality. Stratigraphy: Shuidonggou Formation, Silurian. Sample courtesy of StoneV.
6 – Angers slate, France. Dark and fine-grained slate, with homogeneous texture, very typical in France. It has been quarried for centuries. Startigraphy: Grand-Auverné Formation, Middle Ordovician. Sample courtesy of Ardosieres d´Angers.
And please remember: There are no bad slates but bad uses. The slate should be used in accordance with the building and environment requirements, so it is critical to know and understand the rock we are dealing with.