Nacre stone has been used by a great number of peoples since prehistoric times, since the end of the Palaeolithic. Its iridescent reflections aroused fascination among the First Peoples, who attributed it a symbolic link with the land and the sea. Its uses were numerous :
In addition to these typical uses, some cultures used pearly shells for more specific purposes :
In a more contemporary environment, nacre became more in demand after Elizabeth I gave it the name “Mother of Pearl” in the 15th century, alluding to the similar process of creating pearls and the pearly coating of shells, but also to maternal symbolism. It was then used to make pendants and precious objects of art.
Currently, it is mainly used in jewellery and watchmaking. It is also used in the making of buttons, art objects and marquetry inlays. In jewellery making, it is often associated with onyx, with which it offers a pleasant contrast, onyx being an intense black. In alternative medicine, particularly in Reiki and aromatherapy, some treatments are carried out by the application of seashells, due to their curative properties. They are also used for divination: each shell carries a specific symbolism and message.
Etymologically, the word “nacre” comes from the Arabic word “naqqarah”. Organically, it constitutes the smooth lining of iridescent shine of mollusc shells such as oysters, abalones, mussels… It is biosynthesised by the mollusc mantle, an envelope made up of teguments and muscles which houses the other organs. This mantle secretes the shell. It is formed by a regular juxtaposition of 0.5 µm thick layers of aragonite, welded by a 20 nm thick organic glue, a protein called conchiolin. Conchioline represents a minimal part of the pearly coating (4 to 6%) while aragonite crystals account for more than 90%. When an irritating foreign element penetrates the shell, causing irritation, the molluscs also produce nacre all around to protect themselves from it. Layer after layer, this protection becomes a pearl. Mollusc produces it continuously during its lifetime.
Between the layers of aragonite and conchiolin there are traces of water and various ions: it is their particular arrangement that causes the iridescent reflections, creating interference with light radiation. The reflections depend on the angle of illumination and the position of the observer; the movements of the shell or the observer therefore produce the characteristic iridescence. In addition to these fascinating iridescences, the pearlescent coating may have a special colouring, which varies according to the variety of shell. This colouring comes from the carotenoids contained in conchiolin. Manufacturers have tried to reproduce its special appearance.
From the 17th century onwards, fish scale paints were marketed under the name “Essence of the Orient”. More recently, the plastics industry has used leahd phosphates to give a pearly appearance to buttons. These compounds are toxic and therefore banned for cosmetic use. Other chemical compounds have been developed to copy the pearly iridescent reflections. PW14 is the most frequently used pearlescent pigment at present; it is a bismuth oxychloride. The chemical industry created compounds of mica and metal oxides to provide pearlescent pigments of all dominant colours; this process was patented in 1963. Other chemical processes are used: pearlescent pigments can be made by coating silica or aluminium particles with layers of varying refractive indices. This process creates the light variations that are characteristic of the pearlescent appearance. These pigments are used in cosmetics and in the automotive industry for body paint.
The pearlescent coating of shells is a biomineral; it is produced by the transformation of minerals into a rigid mineral compound from a matrix composed of conchiolin. There are about 60 types of biominerals known to researchers, but it has the particularity of having unique mechanical and physicochemical properties that are very different from other biominerals. One of these peculiarities is its astonishing resistance. It is notably quite resistant to acids and heat. It is more resistant than the shell despite its apparent fragility. It repairs itself after being pierced or damaged when the shell is alive. These unique properties are studied in biochemistry and biomimetics. However, researchers do not know how to reproduce it. The quality and structure of nacre vary according to the shellfish species and the stages of their growth. It is proteins, particularly conchiolin, that structure the pearlescent mineral and confer particular qualities to the pearlescent coating of each shellfish species. The soluble part of conchiolin produces aragonite crystal, while the insoluble part determines the density, size and quantity.
Several varieties of pearly shells exist :
On the psychological level, this stone produces appeasement. It soothes anxieties, anger, tension, mood swings and all excessive emotional states. It acts as a powerful mood regulator for the person who wears it. It releases fears and anxieties that affect daily life. It helps to fight against a negative state of mind. It encourages more measured and thoughtful positions and a calmer and clearer expression of opinions and decisions. Its beneficial side on emotions contributes to a better understanding of oneself and others as well as a capacity to step back from daily life. It is very effective in purifying relational difficulties, especially in love: it promotes communication and more balanced and harmonious relationships. It allows the wearer to be more receptive to the needs of his/her partner. Its soothing side makes it easier to express one’s love feelings and emotions on a daily basis, to express one’s needs and feelings.
On a spiritual and energetic level, it is a powerful stone of intuition and open-mindedness: it stimulates imagination and creativity. It purifies the aura and thus facilitates access to the astral body. It promotes the circulation of energy. By regulating the emotions, it helps to focus the mind and access wisdom and better self-control. It is particularly beneficial to the solar plexus chakra (3rd chakra) and the frontal chakra (6th chakra). Its slow and natural production in an aquatic environment gives it a strong vibratory power and a powerful purifying capacity: the person wearing a pearly object benefits from the energy of the water. It rebalances the energy circulation between body and mind, thus promoting health.
Nacre stone’s regenerative qualities are of particular interest to medical researchers. Indeed, it is said to have a capacity for bone regeneration that is highly sought after in reconstructive surgery. In lithotherapy, this biomineral brings multiple benefits to the health of the person who wears it :