TIGER'S EYE
Tiger's Eye, a popular yet inexpensive gemstone, is a pseudo morph of compact Quartz after the fibrous mineral Crocidolite. It is formed when the Quartz takes over and dissolves the Crocidolite, leaving the Quartz in a finely fibrous and chatoyant form. When polished, it's silky luster creates a beautiful chatoyant effect of moving layers of brown and yellow lines and waves.
Tiger's Eye forms when Quartz forms over existing bluish-gray Crocidolite, and eventually entirely replaces it. Crocidolite is a type of asbestos mineral, which means its composition is of fine, dense fibres. These fibers form in a parallel yet wavy orientation, and this causes the intriguing chatoyant effect exhibited in Tiger's Eye. During the replacementprocess, the iron within the Crocidolite dissolves and stains the Quartz, thereby providing the golden yellow to brown color of the Tiger's Eye.
The original Crocidolite is a bluish-gray color, and sometimes thepseudo orphism to Quartz is incomplete. When this happens, the result is a stone with a bluish-gray color, but still with chatoyant effect. This type of material is known as Hawk’s Eye.
Tiger's Eye may form together with brownish-red or metallic-gray Hematite, or with yellowLimonite, where these minerals forms stripes, streaks, or patterns within the Tiger's Eye. Such material is often called Tiger’s Eye.
Tiger's Eye is a very inexpensive gemstone, and is used in beads for bracelets and necklaces, as well as in pendants. It is also used for costume jewelry and occasionally used for ornate carvings or floral pins. Gemstones cuts of Tiger's Eye are encountered but are not common.
Most Tiger's Eye is natural and not treated. Some of the red or maroon-toned Tiger's Eye is dyed to achieve that color.
Tiger's Eye is a very unique gemstone type and is not easily confused with any other gemstones.
ROSE QUARTZ Ntsako Phakula, group 15. Scientific adviser is Evgenia Grabovetskaya
Rose Quartz, a silicon dioxide crystal, is one of the most common varieties of the Quartz family. Its name is derived from its soft rose color, which ranges from very pale pink to deep reddish-pink. The color is usually considered as due to trace amounts of titanium, iron, or manganese. It usually occurs in massive form, though it sometimes grows in clusters of small prismatic crystals. It varies in clarity from opaque to translucent to a foggy transparency. Some specimens contain traces of Rutile within the stone which creates six-rayed stars when polished into cabochons or spheres and asterism in transmitted light. Recent X-ray diffraction studies suggest that the color is due to thin microscopic fibers of possibly dumortierite within the massive quartz.
Additionally, there is a rare type of pink quartz (also frequently called crystalline rose quartz) with color that is thought to be caused by trace amounts of phosphate or aluminium. The color in crystals is apparently photosensitive and subject to fading. The first crystals were found in a pegmatite found near Rumford, Maine, USA, but most crystals on the market come from Minas Gerais, Brazil.
Rose Quartz is also called Pink Quartz or Hyaline Quartz, from the Greek hyalos, meaning "glass," and was referred to in antiquity as a Bohemian or Silesian Ruby. Rose quartz doesn’t really have any biological effects but in ancient times, it was prized for its powers of beautification. Facial masks of Rose Quartz have been recovered from Egyptian tombs, thought by the Egyptians and Romans to clear the complexion and prevent wrinkles. Rose Quartz was also a stone honored by the Tibetan and Oriental cultures, and continues to be one of the major carving stones of China.
Although it is not popular as a gem because it is generally too clouded by impurities to be suitable for that purpose. Rose quartz is often carved into figures such as people or hearts. Hearts are most commonly found because rose quartz is pink and an affordable mineral.
REFERENCES:
[Ahsian, pp.] Robert Simmons & Naisha Ahsian, The Book of Stones (Berkley, CA: North Atlantic Books, 2007).
[Eason, pp. ]Cassandra Eason, The New Crystal Bible (London: Carlton Books Ltd., 2010).
[Simmons, pp.] Robert Simmons & Naisha Ahsian, The Book of Stones (Berkley, CA: North Atlantic Books, 2007).
MOTHER OF PEARL Osakue Osagioduwa, group 15. Scientific adviser is Evgenia Grabovetskaya
Nacre, or mother of pearl, is a calcium carbonate structure produced by bivalve, gastropods and cephalopods as an internal shell coating. Because of its highly organized internal structure, chemical complexity, mechanical properties and optical effects, which create a characteristic and beautiful lusture, the formation of nacre is among the best studied examples of calcium carbonate biomineralization.
NACRE STRUCTURE: the interdigitating brickwork array of nacre tablet specific in bivalves (sheet nacre) is not only interesting aspect of nacre structure. Nacre is an organo mineral composite at micro and nano scale. The bio crystal itself is a composite.it has not only the mineral structure of aragonite but possesses intra crystalline organic material (watabe, 1965). The primary structure component is a pseudohexagonal tablet, about 0.5 m thick and about 5 to 10 m in width, consisting primarily (97%) of aragonite, a polymorph of CaCO3, and of organics (3%). nacre can be worked as pieces and powder.
BIOLOGICAL ACTION OF RAW NACRE BIOLOGICAL ACTION: A major breakdown was done in 1992, when E.Lopes et al. discovered that natural nacre from the pearl oyster pinctada maxima is simultaneously biocompatible and osteoinductive. Nacre shows osteogenic activity after implantation in human bone environment (silver et al., 1992). Raw nacre pieces designed for large bone defects were used as replacement bone devices in the femur of sheep.over a period of 12 months, the nacre blocks shows persistence without alteration of the implant shape. A complete sequence of osteogenesis resulted from direct contact between newly formed bone and nacre, anchoring the nacre implant (Atlan et al 1997). Furthermore, when nacre is implanted in bone, new bone formation occurs, without any inflammatory reaction and fibrous formation. Results shows calcium and phosphate ions lining the nacre within the osteoprogenitor tissue (Atlan et al 1997).
BIOLOGICAL ACTION OF NACRE EXTRACT: Nacre is composed of aragonite crystal tablets covered by an organic matrix (3%) (Bevelander &Nakahara, 1969).This organic phase is composed of chitine, polysaccharides, proteins, peptides, lipids and other small other molecules lower than 1000Da.the organic molecules can be extracted with aqueous and organic solvent. The water soluble organic matrix dictates which calcium carbonate crystal structure is formed and when it is deposited (Cariolou &Morse,1988).the bulk of water soluble biopolymer is thought to consist of a complex mixture of protein and peptide(Kono et al 2000)
REFERENCES:
Atlan G. et al. interface between bone and nacre implant in sheep.Biomaterials, 20, 1017–1022, 1999.
Atlan G. et al. Reconstruction of human maxillary defects nacre powder:histological evidence for bone regenation.
C R Acad sci paris, life sci, 320, pp.253–258, 1997.
Low molecular weight molecules as new components of the nacre organic matrix.comp biochem physciol B., 144: 532–543, 2006.Bedouet L. et al.
Cariolou M. Morse D. purification and characterization of calcium binding conchiolin shell peptides from mollusk, Haliotis rufescens, as a function of development.
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