Well ... NO!
To understand what clays are and how one type of clay is different from another we have to take a look into their structure at molecular level.
So, if you want to learn some scientific stuff about clays and why they behave like they do, take your time and continue reading about Clay Structure. On the other hand, if scientific stuff is not something you are interested or you think it is too complicated, you can freely skip next paragraph and continue reading at Clay Properties.
There are aproximately 30 types of "pure clays" but only a few are used in cosmetics?
All clays are of mineral origin and common weathering products of rocks rich in silica and aluminium in presence of water. Clays used in cosmetics and skin care are mostly phyllosilicates which mean they are made of small flat crystal sheets. Individual crystals can be made either of silica or aluminium/magnesium, and depending how those crystals are layered there are 2 big groups of clay minerals:
This type of clay mineral is made of 1 layer of silica crystals and 1 layer of aluminium crystals. The best known mineral from this group is kaolinite which forms kaolin clay or china clay. Pure kaolin is mostly white or off white colour. In many parts of the world it is coloured pink, orange or red because of different amounts iron oxide in it.
Kaolin is extremely widely used many industries including pharmaceutical and cosmetic industry.
In this type of clay minerals 1 layer of aluminium or magnesium crystals is sandwiched between 2 layers of silica crystals. Best known minerals from this group are illite and montmorillonite. These clays come with wide variety of other minerals in them thus can be in different colours ranging from grey, green, brown, yellow, etc.
Majority of clays you can buy are this type.
Like we explained in previous paragraph, crystals in clays form fine layers and that is why particles of clay have large specific surface. The thinner the particle edges are specific surface is larger. As a consequence clays have different properties which are called absorption capacity and ion exchange capacity.
Kaolin caly, due to its 1:1 layer structure and stronger bonds between layers forms thicker particles which have smaller specific surface compared to 2:1 clays. That means kaolin cannot absorb large amounts of water and doesn’t swell as much like other clays do, and also, it has lower capacity for ion exchange. On the other hand, montmorillonite and illite clays have much thinner particles resulting in larger specific surface compared to kaolin. Those clays, therefore, can absorb much larger amounts of water and have high capacity for ion exchange.
Large specific surface has several practical consequences and the one of them is ability to bind other substances which is why we use clays in the first place. Different ion exchange capacity has other consequences. Everyone who uses masks knows that, after the clay mask, skin is softened. Apart from just the effect of natural peeling, the skin is softened because clays bind calcium ions from the skin, which is very useful in oily skin. In process of taking calcium from the skin, clay gives the same amount of other important ions (potassium, magnesium, iron, sulphur, etc) from its structure back to the skin.
Do not use clays internaly unless it is clearly alowed on the packaging.
Due to low absorbing and ion exchange capabilities kaolin clays are used to create masks for dry and sensitive skin prone to irritation. We use it when we do not want to be too "rough" for the skin. Kaolin masks are "soft touch" and don’t tighten the skin.
Although kaolin is usually white, some types can be pink or grey depending on other minerals that can be found in them.
Illite clays are most common clay type in cosmetics. Like we already said it is made of 3 layers similar like montmorillonite but layers are here more firmly interconnected. Illite clays swell more than kaolin but less than montmorillonite and the same goes for ion exchange capacity. Masks made from illite clays are therefore more compact, more paste like and easily to prepare than those made from montmorillonite.
Most common type of illite clay is French Green Clay which is considered as the gold standard for masks. Green clay adsorbs impurities and cleans the skin better than kaolin. It is usually used for combination skin but with some additives (small amount of carrier oil) it can easily be applied on dry and sensitive skin too. Illite clays can be found in different colour types and are then marketed for different purposes.
Talcum is similar in structure to illite, but has mostly magnesium instead of aluminium crystals. Due to its characteristics it is not suitable for masks but only for dry powders.
They are similar in structure to illite but here layers are only loosely interconnected and that allows them to both adsorb and absorb large amount of water and other minerals. Therefore montmorillonite clays swell a lot and have very high ion exchange capacity. The most famous representative of montmorillonite clays is Bentonite.
Bentonite masks are softer and more gelatinous so they are often mixed with illite clays to make them lighter on skin. Because it has very high ion exchange capacity, bentonite is commonly used for oily skin or it is added to other clays to enhance its adsorbing and detox properties.
Kaolin clays are low adsorbing and are used for dry or normal skin.
Bentonite clays are highly adsorbing and are used for oily skin.
Illite clays are somewhere in the middle and can be used for all skin types
CLAY COMBINATIONS ON THE MARKET
Often clays get their name after geographical location where it was found. Because of changing rock deposits in different areas of the world clays are often not clean but naturally mixed. That is why you can found for example Australian Pink Clay, Brazilian Clay, Multani Mitti, Rhassoul Clay, etc. From those names you certanly can not distinguish what certain clay is good for so we recommend to always look for label where that information should be written.
Australian Pink Clay, is kaolin with small amount of iron oxides. The same goes for Brazilian clays. Those clays, if not mixed with other types of clays, are suitable for normal or dry skin, and their have different colors due to different other minerals present.
Fuller’s Earth or Multani Mitti is well known combination of bentonite and other clay minerals. It has high capacity for binding oils and colors and from liquids. Those properties make it effective on human hair and skin. Since ancient times it has found extensive uses in the beauty industry, both as a cosmetic and as a treatment for acne and other skin problems. Some types have antiseptic properties, which enhance their effectiveness as skin treatments, but not all though not all forms of Fuller’s earth are truly antiseptic. It is common mask ingredient in India but in other parts of the world it is now rarely used.
Rhassoul clay, also called Ghassoul, is found and naturally mined exclusively in the Atlas mountain of Morocco. It is volcanic clay composed of specific illite and magnesium montmorillonite minerals and contains silica, iron, magnesium, potassium, sodium, lithium, and many other trace elements. Thanks to its exceptional ability to absorb impurities without irritating the skin, rhassoul is traditionally used for preparing mild and purifying products that does not irritate the sebaceous glands and can be used for all skin and hair types.