- Pyrope
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Pyrope 
A gem-quality, emerald cut pyrope.General Category Nesosilicate Chemical formula Mg3Al2(SiO4)3 Strunz classification 09.AD.25 Identification Color Red. Some varieties are very dark, almost black, while others can take tones of purple. Some chromium-rich pyropes are thermochromic, becoming green when heated[1] Crystal habit Euhedra typically display rhombic dodecahedral form, but trapezohedra are not uncommon, and hexoctahedra are seen in some rare samples. Massive and granular forms also occur. Crystal system Cubic Cleavage None Fracture Conchoidal Mohs scale hardness 7 - 7.5 Luster greasy to vitreous [2] Streak White Specific gravity 3.78 (+.09 -.16) [2] Polish luster vitreous[2] Optical properties Single refractive, often anomalous double refractive [2] Refractive index 1.74 normal, but ranges from 1.714 to over 1.742 [2] Birefringence Isotropic, appears black in cross-polarized light Pleochroism none Ultraviolet fluorescence inert Absorption spectra broad band at 564nm with cutoff at 440 to 445nm. Fine gem quality pyropes may show chromium lines in the red end of the spectrum Solubility Insoluble in water, weakly soluble in HF Mineral association Olivine, pyroxene, hornblende, biotite, diamond - This article is about the mineral. For the bird sometimes placed in the monotypic genus Pyrope, see Fire-eyed Diucon.
The mineral pyrope is a member of the garnet group. Pyrope is the only member of the garnet family to always display red colouration in natural samples, and it is from this characteristic that it gets its name: from the Greek for fire and eye. Despite being less common than most garnets, it is a widely used gemstone with numerous alternative names, some of which are misnomers. Chrome pyrope, and Bohemian garnet are two alternative names, the usage of the later being discouraged by the Gemological Institute of America.[2] Misnomers include Colorado ruby, Arizona ruby, California ruby, Rocky Mountain ruby, Elie Ruby, Bohemian carbuncle, and Cape ruby.
A distorted, euhedral, dodecahedral pyrope crystal, from Madagascar.
The composition of pure pyrope is Mg3Al2(SiO4)3, although typically other elements are present in at least minor proportions -- these other elements include Ca, Cr, Fe and Mn. Pyrope forms a solid solution series with almandine and spessartine, which are collectively known as the pyralspite garnets (pyrope, almandine, spessartine). Iron and manganese substitute for the magnesium in the pyrope structure. The resultant, mixed composition garnets are defined according to their pyrope-almandine ratio. The semi-precious stone rhodolite is a garnet of ~70% pyrope composition.
The origin of most pyrope is in ultramafic rocks, typically peridotite from the Earth's mantle: these mantle-derived peridotites can be attributed both to igneous and metamorphic processes. Pyrope also occurs in ultrahigh-pressure (UHP) metamorphic rocks, as in the Dora-Maira massif in the western Alps. In that massif, nearly pure pyrope occurs in crystals to almost 12 cm in diameter; some of that pyrope has inclusions of coesite, and some has inclusions of enstatite and sapphirine.
Pyrope is common in peridotite xenoliths from kimberlite pipes, some of which are diamond-bearing. Pyrope found in association with diamond commonly has a Cr2O3 content of 3-8%, which imparts a distinctive violet to deep purple colouration (often with a greenish tinge) and because of this is often used as a kimberlite indicator mineral in areas where erosive activity makes pin pointing the origin of the pipe difficult. These varieties are known as chrome-pyrope, or G9/G10 garnets.
Contents
Mineral identification
Pyrope aggregate.In hand specimen, pyrope is very tricky to distinguish from almandine, however it is likely to display fewer flaws and inclusions. Other distinguishing criteria are listed in the table to the right. Care should be taken when using these properties as many of those listed have been determined from synthetically grown, pure-composition pyrope. Others, such as pyrope's high specific gravity, may be of little use when studying a small crystal embedded in a matrix of other silicate minerals. In these cases, mineral association with other mafic and ultramafic minerals may be the best indication that the garnet you are studying is pyrope.
In petrographic thin section, the most distinguishing features of pyrope are those shared with the other common garnets: high relief and isotropy. Garnets tend to be less strongly coloured than other silicate minerals in thin section, although pyrope may show a pale pinkish-purple hue in plane-polarized light. The lack of cleavage, commonly euhedral crystal morphology, and mineral associations should also be used in identification of pyrope under the microscope.
Health effects
Magnesium aluminum silicate powder is a common ingredient in makeup, pesticide, pharmaceuticals, and other products. Specific health effects depend upon the size, shape, and amount when dust particles are lofted into the air. Fine powder forms clay when water is added. Studies do not exist that indicate increase risk of cancer.
Magnesium aluminum silicate is not considered to be a hazardous substance by US Department of Transportation and US Environmental Protection Agency, and it is not considered to be carcinogenic under California Proposition 65.
Aluminum is one of the non-protein components of amyloid plaque associated with Alzheimer's disease. Silicon is associated with increase risk of cancer and osteoporosis. Magnesium aluminum silicate contains both.[3][4][5]
Do not breathe dust. If ingested, seek medical advice immediately and display the container or label to physicians. Respirators are required to prevent inhalation. The treatment after inhalation is to keep airways open and provide oxygen.[6][7] A self contained breathing apparatus should be used to avoid dust inhalation.[8][9]
The following are required for large spills.
- Splash goggles.
- Full suit.
- Dust respirator.
- Boots.
- Gloves.
There are several forms, and magnesium aluminum silicate may be identified by several different CAS#, such as 12174-11-7, 1327-43-1, and 12199-37-0.[10][11][12]
Inhaling finely divided dust particles in very small quantities over time can lead to bronchitis, emphysema, or other diseases as the dust becomes lodged in the lungs, reducing lung capacities. In the body, magnesium aluminum silicate particles dissolve slowly and may form mud, which may be expectorated from the lungs and ingested. This exposes the body to silicon and aluminum that can pose health risks. Children, asthmatics of any age, allergy sufferers, and the elderly (all of whom have reduced lung capacity) can be affected in much less time.[13][14][15]
Names
The following names may be used to describe silica dust.
Aluminosilicic acid, magnesium salt Magnesium Aluminometasilicate Attapulgite Magnesium Aluminum Silicate Type 1A Smectite Clay Palygorskite SAluminum Magnesium Silcate Type 1A Veegum Pyrope Inhalation Risks
- Alzheimer's: Respirable and ingested magnesium aluminum silicate may contribute to Alzheimer's disease.[16][17]
- Osteoporosis: Respirable and ingested magnesium aluminum silicate may contribute to osteoporosis.[18]
- Non-Malignant Respiratory Diseases (other than silicosis): Some studies show an increased incidence of chronic bronchitis and emphysema associated with magnesium aluminum silicate[19][20]
Eye Contact
Magnesium aluminum silicate may cause eye irritation. In case of contact, immediately flush eyes with plenty of water for at least 15 minutes and seek medical attention.[21][22]
References
- ^ Thermochromic Cr-rich Pyrope Garnets
- ^ a b c d e f (Gia), Gemological. Gem Reference Guide. City: Gemological Institute of America (GIA), 1988. ISBN 0-87311-019-6
- ^ "Silicon and Bone health". National Library of Medicine. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658806/.
- ^ "Analysis of the biological and chemical reactivity of zeolite-based aluminosilicate fibers and particulates". National Library of Medicine. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1241064/.
- ^ "Neuronal origin of a cerebral amyloid: neurofibriliary tangles of Alzheimer's disease contain the same protein as the amyloid of plaque cores and blood vessels". National Library of Medicine. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC554575/pdf/emboj00276-0041.pdf.
- ^ {{cite web|url=http://www.bayerdvm.com/products/tempo/tempo-20.cfm%7Ctitle=Tempo 20 MSDS|publisher=Bayer DVM}
- ^ "Magnesium Aluminum Silicate; MSDS". Science Lab. http://www.sciencelab.com/msds.php?msdsId=9924536.
- ^ {{cite web|url=http://www.bayerdvm.com/products/tempo/tempo-20.cfm%7Ctitle=Tempo 20 MSDS|publisher=Bayer DVM}
- ^ "Magnesium Aluminum Silicate; MSDS". Science Lab. http://www.sciencelab.com/msds.php?msdsId=9924536.
- ^ {{cite web|url=http://www.bayerdvm.com/products/tempo/tempo-20.cfm%7Ctitle=Tempo 20 MSDS|publisher=Bayer DVM}
- ^ "Magnesium Aluminum Silicate; MSDS". Science Lab. http://www.sciencelab.com/msds.php?msdsId=9924536.
- ^ "Magnesium Aluminum Silicate; MSDS". Science Lab. http://www.sciencelab.com/msds.php?msdsId=9924536.
- ^ "Silicon and Bone health". National Library of Medicine. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658806/.
- ^ "Analysis of the biological and chemical reactivity of zeolite-based aluminosilicate fibers and particulates". National Library of Medicine. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1241064/.
- ^ "Neuronal origin of a cerebral amyloid: neurofibriliary tangles of Alzheimer's disease contain the same protein as the amyloid of plaque cores and blood vessels". National Library of Medicine. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC554575/pdf/emboj00276-0041.pdf.
- ^ "Neuronal origin of a cerebral amyloid: neurofibriliary tangles of Alzheimer's disease contain the same protein as the amyloid of plaque cores and blood vessels". National Library of Medicine. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC554575/pdf/emboj00276-0041.pdf.
- ^ "Link between Aluminum and the Pathogenesis of Alzheimer's Disease: The Integration of the Aluminum and Amyloid Cascade Hypotheses". National LIbrary of Medicine. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3056430/.
- ^ "Neuronal origin of a cerebral amyloid: neurofibriliary tangles of Alzheimer's disease contain the same protein as the amyloid of plaque cores and blood vessels". National Library of Medicine. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC554575/pdf/emboj00276-0041.pdf.
- ^ "Analysis of the biological and chemical reactivity of zeolite-based aluminosilicate fibers and particulates". National Library of Medicine. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1241064/.
- ^ "Final report on the safety assessment of aluminum silicate, calcium silicate, magnesium aluminum silicate, magnesium silicate, magnesium trisilicate, sodium magnesium silicate, zirconium silicate, attapulgite, bentonite, Fuller's earth, hectorite, kaolin, lithium magnesium silicate, lithium magnesium sodium silicate, montmorillonite, pyrophyllite, and zeolite". National Library of Medicine. http://www.ncbi.nlm.nih.gov/pubmed/12851164.
- ^ {{cite web|url=http://www.bayerdvm.com/products/tempo/tempo-20.cfm%7Ctitle=Tempo 20 MSDS|publisher=Bayer DVM}
- ^ "Magnesium Aluminum Silicate; MSDS". Science Lab. http://www.sciencelab.com/msds.php?msdsId=9924536.
- STEHLÍKOVÁ, Dana: The Bohemian Garnet, 1. Aufl. Nationalmuseum Prague 2003; 2.Aufl., Prague - Cedar Rapids (Iowa) 2004
Categories:- Magnesium minerals
- Aluminium minerals
- Garnet group
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