What Shade Is Clay?

Clay is a naturally occurring fine-grained soil that forms from the weathering and erosion of rocks. It is composed primarily of hydrated aluminum silicates, often with traces of iron, magnesium, alkali metals, alkaline earths and other compounds.

The most common types of clay include kaolinite, montmorillonite-smectite, illite, and chlorite. Clays are plastic due to their chemical structure and are moldable and workable in their wet state. When fired at high temperatures, clay becomes permanently hard and brittle. This makes clay a versatile material used for pottery, ceramics, bricks, cement, and other applications.

The composition and properties of clay determine its color, texture, plasticity, shrinkage, porosity, and strength when fired. Understanding the nature and shade of different clays is key to selecting the appropriate type of clay for its intended use.

Natural Clay Colors

There are many natural colors of clay based on the mineral content and other elements present in the soil. Some of the most common natural clay colors include:

Red Clay

Red clay gets its color from iron oxide. The high iron content gives red clay its distinctive red hue. Red clay is commonly found in tropical areas with warm climates. According to this Reddit thread, red clay often has shiny mica bits visible which add sparkle and interest to the natural color.

White Clay

White clay, also known as kaolin or china clay, gets its white color from the mineral kaolinite. Kaolinite clay is very pure in composition and is bright white when raw. The largest deposits of white clay are found in tropical, humid climates.

Grey Clay

Grey clay gets its color from a blend of other minerals like silica and iron. The combination creates a more muted, greyish tone rather than a bright red or white. Grey clay is commonly found in areas with moderate rainfall and diverse mineral deposits.

Red Clay

Red clay gets its distinctive red color from iron oxide. The concentration and type of iron oxide determines the exact shade, which can range from orangey red to deep burgundy. Red clay deposits are found across the world, often in tropical regions. The soil tends to be quite acidic due to the iron content. It also has good moisture retention properties.About — Red Clay Strays

Red clay is used for a variety of purposes. It is a common material for making pottery due to its excellent plasticity and firing qualities. When fired at high temperatures, the clay hardens into a durable, terracotta material. Unfired red clay is also used to make bricks and floor tiles. In construction, red clay serves as a key ingredient in mortar mixes and wall plasters. It provides the distinctive red hue in Spanish roofing tiles. Red clay is also used to line landfill sites due to its low permeability.Red Clay

In skincare and cosmetics, red clay has an array of uses. It can be applied as a purifying face mask or added to baths and scrubs. The iron oxides provide antioxidant and anti-inflammatory properties while the clay draws out impurities. Some cultures consume red clay for its perceived digestive and wellness benefits.Inside Red Clay

White Clay

White clay refers to kaolin clay, which is named after the Kao-ling mountain in China where this type of clay was first mined (https://peterpugger.com/2018/03/28/what-you-need-to-know-about-porcelain/). Kaolin clay is created by the natural weathering of feldspar rocks, which gives it a white hue. The particle size of kaolin clay is very small, giving it a fine, smooth texture.

Some key properties of white kaolin clay include its brightness, whiteness, chemical purity, and resistance to high temperature. This makes it ideal for use in ceramics, paper, paint, plastic, concrete, pharmaceuticals, and cosmetics. White kaolin clay is sometimes called “China clay” because it was first used in ancient China to create fine porcelain.

Today, kaolin clay is commercially mined in many parts of the world including Australia, Brazil, and the United States. The largest use of kaolin worldwide is in paper production, where it gives glossiness, brightness, and ink absorbency. It is also a critical ingredient in porcelain and china. Kaolin’s whiteness, neutral color, and chemical inertness make it an ideal mineral for a variety of consumer products and industrial uses (https://www.businesswire.com/news/home/20230601005240/en/White-Clay-Launches-Treasury-Management-Pricing-and-Profitability-Solution).

Grey Clay

Grey clay gets its color from a high concentration of organic matter mixed with the clay particles. According to the report from the Department of Primary Industries and Regional Development, “About Grey Clay Soils,” grey clay soils are common in seasonally waterlogged areas and floodplains across Western Australia (Managing grey clays).

The topsoil of grey clay areas tends to be darker due to accumulated organic matter. The subsurface is lighter grey. Grey clays have poor structure and low permeability. They are sticky when wet and hard when dry. Grey clays are used to make bricks and lightweight aggregate. Improving drainage and adding organic matter can help make grey clays more manageable for agriculture and construction.

Brown Clay

Brown clay is an iron-rich clay that gets its distinctive brownish hue from iron oxide. It is formed through the weathering and decomposition of rocks that contain iron minerals like hematite, maghemite, or goethite. The iron leaches out during the weathering process and oxidizes, giving the clay its characteristic brownish or reddish-brown coloration (https://encyclopedia2.thefreedictionary.com/brown+clay).

The properties of brown clay depend on the exact mineral composition but in general it has good plasticity and firing properties. The high iron content gives it a sandy texture and makes it easier to work with than more dense clays. When fired, brown clay acquires an earthy red-brown color. Due to the high iron content, brown clays also fire at slightly lower temperatures than other clay bodies (https://www.colorxs.com/color/brown-clay-ppg1199-6).

Brown clay has many uses, especially in ceramics and pottery. The iron oxide content gives the finished pieces a distinctive reddish-brown hue when fired that is prized in stoneware and earthenware pottery. Brown clay can be used on its own or blended with other clays. It works well for handbuilding techniques like coil building and slab work. Brown clay is also sometimes used as a natural pigment in paints, cosmetics, and construction materials.

Green Clay

Green clay, also known as French green clay or montmorillonite, is a naturally occurring clay that gets its green color from decomposed plant matter and iron oxide. It comes from natural deposits in France and has been used for centuries for skin and health purposes (https://www.biocoiff.com/en/vertus-bienfaits-argile-verte/).

Green clay is derived from naturally occurring montmorillonite, a very soft phyllosilicate mineral that forms when volcanic ash ages in ocean water. It has a layered structure that can absorb large amounts of water. The absorptive properties give green clay the ability to draw out toxins, oils, and impurities when applied topically (http://thetoxicfreefoundation.com/database/ingredient/green-clay-minerals).

Thanks to its mineral content, green clay has clarifying, soothing, and toning properties when used on the skin. It is often used in skincare products like face masks, cleansers, and scrubs to help clear acne, balance oily skin, minimize pores, and improve overall complexion. It can also be used in hair masks and treatments (https://kataribeauty.com/products/argil).

Some proponents believe consuming green clay can provide internal detoxification and gastrointestinal benefits, though research is limited in this area. Topically, green clay is generally considered safe for most people when used as directed.

Blue Clay

Blue clay gets its distinctive blue-gray color from the presence of certain minerals, particularly vivianite, a hydrated iron phosphate mineral that forms in anaerobic and acidic conditions. The lack of oxygen causes the iron in the clay to become reduced, taking on a bluish hue (1). Vivianite is found in clay deposits around the world, including France, where it was originally discovered and named. Other minerals that can contribute to blue clay’s coloration include azurite, a basic copper carbonate, and glauconite, an iron potassium phyllosilicate (2).

Due to its high iron content, blue clay is believed to stimulate circulation, remove toxins, and provide nutritional benefits when used topically or internally. It is sometimes marketed as a health and beauty product. Blue clay also has absorbent properties and can be used in soaps, skin care products, and cat litter (3). When fired at high temperatures, it can produce a terra cotta or brownish ceramic ware.

In 2012, the French Open tennis tournament experimented with using blue clay courts instead of the traditional red clay. However, many players complained that the blue courts were too slippery. As a result, they reverted to red clay the following year (1).

(1) http://tt.tennis-warehouse.com/index.php?threads/blue-clay-what-was-the-problem.527786/
(2) https://permies.com/t/28669/Blue-clay

(3) https://www.treasurenet.com/threads/blue-clay-minerals.671859/

Purple Clay

Purple clay, sometimes called Zisha clay, gets its distinctive color from iron oxide. This type of clay is found in the Yixing region of China, which has become renowned for purple clay teapots.¹ The clay has naturally high iron content which turns purple when fired under high temperatures.

Purple clay is prized for its ability to absorb tea flavors and improve the taste of the tea. The porous nature of the clay allows it to absorb the oils and flavors from tea, and impart those flavors back into the tea during brewing. This helps mellow and soften the taste of the tea. Purple clay teapots are also admired for their artisanal look and natural beauty.

In addition to teapots and tea accessories, purple clay is also used to make Yixing clay figurines and other decorative items. The natural color and artistic possibilities make it a popular clay for potters and artisans.

Conclusion

In summary, clay comes in a diverse array of natural shades that potters can utilize for different purposes. The most common clay colors and their associated uses are:

Red clay – Known for its rich terracotta tones, red firing clay is ideal for flower pots, garden pots, decorative items, and sculptures. Its high iron content gives it a rustic, earthy look.

White clay – Valued for its bright white color when fired, white clays like kaolin or ball clay allow potters to create porcelain with a clean, pure aesthetic. White clay is perfect for dinnerware, tiles, and delicate pieces.

Grey clay – The neutral grey tones of stoneware clay make it extremely versatile. Grey clay is commonly used for oven-safe dishes, mugs, vases, and other functional pottery requiring durability.

Brown clay – Containing natural impurities like iron oxide, brown clays like earthenware produce pottery with warm earth tones. Brown clay works well for flower pots, garden art, and rustic home decor.

Knowing the unique properties and best uses for different clay colors gives potters the ability to select the right material for any project.