Mother of pearl
Mother of pearl , also mother-of-pearl (cf. English Mother of pearl ), from Middle High German berlīnmuoter (the inner, pearl-like layer of the shell of various molluscs, especially sea and pearl mussels), translation from Latin mater perlarum (shell containing a pearl).
It is a natural composite material of calcium carbonate and organic substances that forms the innermost layer (“hypostracum”) or the entire predominantly mineral part of the shell of certain mollusks . Due to its special surface structure, which creates a matt, iridescent sheen when exposed to light , it is used in the production of art objects such as B. Jewelry and decorative buttons.
Occurrence
Nacre is supported by numerous mollusks deposited to build their shells, in particular from the pteriiden mussels with, among others, the pearl oysters ( Pinctada ), and by the trochidae (Trochidae), the turban or round snails (Turbinidae), the abalone ( Haliotis , also called "abalone "Called) and the pearl boats ( Nautilus , also called" Burgos "), which belong to the cephalopods . The colors of mother-of-pearl differ depending on the species and geographical origin.
construction
General
The Biomineralisat nacre is at least 95% (mass fraction) of the inorganic chemical compound calcium carbonate (CaCO 3 ) in the modification aragonite . Up to five percent consist of organic matter. The aragonite is in the form of pseudo- hexagonal platelets with a diameter of 5–15 µm and a height of 0.5 µm. These aragonite plates are put together horizontally (in the shell plane) to form individual layers. Vertically (at right angles to the shell level) the platelets in mussels are more like brick-like alternating, in snails they are arranged in stacks. The so-called organic matrix extends between the individual platelets both in the shell plane and perpendicular to it.
Organic matrix
The organic matrix is responsible for the growth and mechanical properties of mother-of-pearl. The structure and role of the organic matrix during mother-of-pearl growth is intensively researched. It is usually divided into the water-insoluble and water-soluble matrix, depending on how the organic components behave after the demineralization of the mother-of-pearl.
The water-insoluble matrix is the material that is located vertically (interlamellar matrix) and laterally (intertabular matrix) between the platelets. The interlamellar matrix is approx. 30–50 nm thick and has a core made of chitin . This chitin is coated on both sides with various proteins, including silk fibroin. The intertabular matrix is thinner than the interlamellar, but also consists of chitin and proteins.
The water-soluble matrix consists of a number (> 10) of proteins, some of which have a strong influence on the crystallization of calcium carbonate.
Optical properties
The layer structures are in the order of magnitude of the wavelength of visible light . Since part of the incident white light is transmitted and part reflected on each layer , interference occurs : Incident and reflected light rays overlap in such a way that certain parts of the spectrum of the white light are deleted and, depending on the viewing angle, different color tones remain (see also Bragg equation ). If the mother-of-pearl is moved in the light, it therefore seems to shimmer ( iridescent ).
Mechanical properties
Mother-of-pearl is a composite material that can be thought of as a brick wall. Due to the organic material (" mortar ") between the hard but brittle aragonite platelets (" bricks "), cracks can only spread with high energy expenditure.
use
The ground and polished shells of the pearl oysters were a common currency material e.g. B. in the Polynesian world. Even today they have such a status in isolated cases. Mother-of-pearl chips were another form of currency in many European casinos until the end of the 19th century.
Mother-of-pearl has long been used to make jewelry because of its iridescent optical properties . Mother-of-pearl buttons are often used for high-quality shirts and blouses . In the northern Thuringian city of Bad Frankenhausen there was a flourishing mother-of-pearl button production in the 19th century.
To decorate furniture and wooden boxes ( inlays ), in addition to veneers made of precious wood , plates made of mother-of-pearl were also used. Mother-of-pearl plays a major role in Chinese lacquer art .
Mother-of-pearl is still used today in the construction of musical instruments. For example, it is used in the construction of guitars and basses as a fingerboard insert for orientation - so-called “inlays” in the form of blocks, points or images (e.g. of birds). The frog eyes and drawers of the bows of string instruments are often made of mother-of-pearl. White or black mother-of-pearl is also used for the inlays of the keys on high-quality saxophones and brass instruments .
In the past, mother-of-pearl fishing lures were in use. The prismatic shimmer successfully faked a small delicacy for many predatory fish species. Anglers also liked these mother-of-pearl baits, as mother-of-pearl is heavy enough to be carried far (enough) out into the lake or sea with the rod and fishing line.
Mother-of-pearl is an advantage as a material for making spoons because it is tasteless in contact with eggs or caviar .
It is investigated whether artificially produced mother-of-pearl, pearloid (English pearloid ) is suitable as a corrosion-resistant protective layer on ship hulls.
Web links
- Vivienne Baillie Gerritsen (proteinspotlight): String of intrusion , accessed on September 14, 2012.
Single receipts
- ↑ Jürgen Martin: The 'Ulmer Wundarznei'. Introduction - Text - Glossary on a monument to German specialist prose from the 15th century. Königshausen & Neumann, Würzburg 1991 (= Würzburg medical-historical research. Volume 52), ISBN 3-88479-801-4 (also medical dissertation Würzburg 1990), p. 117.
- ^ Friedrich Kluge: Etymological dictionary of the German language. 22nd edition. 1989, ISBN 3-11-006800-1 , p. 536.
- ↑ Katharina Gries: Investigations of the formation processes and the structure of the mother-of-pearl of abalons. Dissertation, University of Bremen, 2011 ( PDF 25.4 MB).
- Jump up ↑ Yael Levi-Kalisman et al .: Structure of the nacreous organic matrix of a bivalve mollusk shell examined in the hydrated state using cryo-TEM. In: Journal of Structural Biology. Volume 135, No. 1, 2001, pp. 8-17, doi: 10.1006 / jsbi.2001.4372 .
- ↑ Ellen C. Keene, John S. Evans and Lara A. Estroff: Silk fibroin hydrogels coupled with the n16N − β-chitin complex: An in vitro organic matrix for controlling calcium carbonate mineralization. In: Crystal Growth & Design. Volume 10, No. 12, 2010, pp. 5169-5251.