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Slate - Type of Stone

Staff Writer
December 27, 2022
Staff Writer
December 27, 2022
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Slate is made from low-grade metamorphic mudrock that has been put through immense heat and pressure to create the slate we know today. It can take up to millions of years to form slate, and some varieties may be made from volcanic ash from the prehistoric eras. 

The stone contains several traces of minerals, mainly chlorite, quartz, and illite. Other accessory minerals include iron oxides and iron sulfides like hematite and pyrite, respectively. The rough texture of the material is called the slaty cleavage, which is formed due to the presence of the microscopic minerals in the composition of the stone. 

Slate is typically gray in color, but can form other tones depending on its locality. The main uses of the rock are for roofing tiles, and slate was the popular stone of choice for announcement boards for pubs, bars, and inns, eventually coining the term blank slate.


Slate stone can be traced back to millions of years ago. The fine-grained stone started off as clumps of volcanic ash, which then underwent metamorphic heat and pressure to solidify, changing to the rock-hard composition known as slate today. 

Before the mid-19th century, slate was indistinguishable from other forms of rock used in architectural and commercial uses. Slate was often used interchangeably with shale and schist, which are similar stones of clay and ash origins. However, the mineral composition of the three stones determined their durability, and so slate eventually became its own category.

The term slate continues to be used to describe similar-looking rocks of unknown composition. In scientific papers, slate can refer to stones of similar origin, but of unknown properties before the rock is classified otherwise. In architecture, on the other hand, slate is the term used for roof shillings, regardless of the material. 


Slate typically grows as a gray rock that can range from medium gray to dark gray, and may or may not have subtle blue hues to the rock. Depending on its locality, slate can take on hues of green, purple, and teal - particularly in slate stone found in North Wales. 

The surface of the slate stone is rough and ragged, characteristic of the stone. Many architectural designers prefer slate over smooth rocks for a rustic and natural feel of the home, complete with a natural stone design on rooftops, driveway tiles, and more.

Beneficial Features of Slate

Despite the fact that slate is a common form of stone material, its beneficial properties weigh in more than stones of similar origin. Slate is weather-proof, fire-proof, and resists water absorption well, making the stone perfect for outdoor use.

One of the reasons why slate is commonly used in roof tiles is that slate has the unique property to withstand various weather conditions such as UV rays, rain, snow, and winds. The average lifespan of a slate roofing material can go up to 125 years, so many homeowners continue to prefer slate roofing over other materials for its durability.

Uses of Slate

In the 19th to early 20th century, slate was used in place of modern chalkboards, where notices and announcements were scrawled on using chalk. The rough texture of slate, coupled with its abundance in quarries, made the stone a popular choice of material for commercial uses. Bar tabs would be monitored on a slate board, which is where the term clean slate came from. 

Today, modern uses for slate include roof shillings, outdoor tiles, and as flooring for driveways. The rustic feel of slate contributes to its appropriateness to outdoor use, as the slaty cleavage provides a non-slip grip during rainy days. The stone is also water-resistant, and does well under weather conditions like snow and shine. 

Other known uses for slate include tombstones, ritualistic tablets, table coasters, and stone decorations in botanic gardens. Stone benches may also be made from slate, as the material is sturdy and functional. Slate has found modern use in food photography and presentation as well, giving a rustic yet sophisticated feel to the food.

The natural gray hues of the stone gives it a natural feel, and broadens its scope of applications throughout residential and commercial uses. With the rise of natural aesthetics and Nordic designs, slate has become an accent piece for indoor use as well as outdoor use, with rustic slate countertops, bathroom tiles, indoor fountains, and decorative sinks becoming a trend.

Care Instructions

Slate is fairly easy to maintain. In fact, the stone hardly needs any cleaning and maintenance at all. The stone is stain resistant, so there is no need for intense scrubbing or cleaning. General cleaning is recommended for slate flooring, particularly for outdoor areas. 

Slate can be easily cleaned with a strong jet of water from a hose or a pressure washer. Mild soap solution can be used to get rid of any moss that has grown in the porous surface of the slate material, and the stone can be set out to air dry under the sun. 

Scratches may become a problem for slate, as the material is used in outdoor locations where the stone is subject to natural forces. Scratches may not deteriorate the composition of the material, but it can eventually cause cracks and affect the overall appearance of the stone.

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Staff Writer

Staff Writer

This article is written by our passionate staff writers who seek to share our knowledge from our business

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