Slate Formation, Hardness, Composition
· Slate is a beautiful, durable, and versatile natural stone used in constructing roofs, flooring, and flagging.
· It is formed through low-grade metamorphism of clay, sedimentary rock shale, or volcanic ash containing mica, chlorite, quartz, and other minerals.
· It is cut into thin slabs and comes in varying colors.
· It is widely used in construction due to its fireproof, stain, wind, moisture resistance, and sound-insulating properties.
· The quarries are located in the United States, Europe, and Brazil.
· It is a widely used natural stone famous for its practicality, easy maintenance, and beautiful appearance.
Formation
Slate is formed from the metamorphosis of mudstone or shale under low-pressure conditions.
When shale or mudstone is exposed to heat and pressure from tectonic plate activity, its clay minerals transform into mica minerals. Biotite, chlorite, and muscovite are the main components of slate.
· Foliation is a unique characteristic of slate, referring to the repetitive lamination of metamorphic rocks caused by shearing forces or differential pressure.
· Layers of rocks are formed perpendicular to the direction of the pressure of metamorphic compression, allowing slate to cleave along flat planes.
Hardness
The Mohs scale is used to measure the hardness of minerals.
Slate has a hardness of 2.5 to 4 on this scale, making it almost as hard as marble and limestone but not as hard as granite or natural quartz.
Dimension and Crushed Slate
Dimension slate and crushed slate (granules and flour) are two types of slate marketed.
· Dimension slate is commonly used for electrical panels, laboratory tabletops, roofing and flooring, and blackboards.
· On the other hand, Crushed slate is used on composition roofing, in aggregates, and as a filler.
Composition
· Slate is mainly composed of quartz, illite, and chlorite, making up 95% of its composition.
· Accessory minerals such as iron oxides (hematite and magnetite), iron sulfides (pyrite), and carbonate minerals are also essential.
· Apatite, graphite, kaolinite, magnetite, tourmaline, and feldspar are sometimes present, although less frequently.
