# Pyrope > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Pyrope > Markdown URL: https://mediated.wiki/source/Pyrope.md > Source: https://en.wikipedia.org/wiki/Pyrope > Source revision: 1348180678 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Mineral of the garnet group}} {{about|the mineral|the bird sometimes placed in the monotypic genus ''Pyrope''|Fire-eyed diucon|the ''[Homestuck](/source/Homestuck)'' character|Terezi Pyrope}} {{Infobox mineral | name = Pyrope | category = [Nesosilicate](/source/Nesosilicate) | boxwidth = | boxtextcolor= #FFFFFF | boxbgcolor = #270000 | image = Pyrope-260132.jpg | imagesize = | caption = | strunz = 9.AD.25 | formula = Mg3Al2(SiO4)3 | IMAsymbol = Prp{{Cite journal|last=Warr|first=L. N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3 |pages=291–320|doi=10.1180/mgm.2021.43 |bibcode=2021MinM...85..291W |s2cid=235729616 |doi-access=free}} | molweight = | system = [Cubic](/source/Cubic_crystal_system) | class = Hexoctahedral (m{{overline|3}}m)
[H–M symbol](/source/H%E2%80%93M_symbol): (4/m {{overline|3}} 2/m) | symmetry = ''Ia''{{overline|3}}d | color = Blood red to black red, red, orange red, pink, some varieties are very dark, almost black, while others can take tones of purple to purple red, Some [chromium](/source/chromium)-rich pyropes are [thermochromic](/source/thermochromic), becoming green when heated.[http://minerals.gps.caltech.edu/mineralogy/undergrad/garnet_2001/garnet.html Thermochromic Cr-rich Pyrope Garnets] | habit = [Euhedra](/source/Euhedral) typically display [rhombic dodecahedral](/source/Rhombic_dodecahedron) form, but [trapezohedra](/source/Trapezohedron) are not uncommon, and hexoctahedra are seen in some rare samples. Massive and granular forms also occur. | twinning = | cleavage = None | fracture = [Conchoidal](/source/Conchoidal_fracture) | mohs = 7.0–7.5 | luster = greasy to vitreous | polish = vitreous | refractive = 1.74 normal, but ranges from 1.714 to over 1.742 | opticalprop = Single refractive, often anomalous double refractive | birefringence = [Isotropic](/source/Isotropy), appears black in cross-polarized light | dispersion = | pleochroism = none | fluorescence= inert | absorption = broad band at 564 nm with cutoff at 440 to 445 nm. Fine gem quality pyropes may show [chromium](/source/chromium) lines in the red end of the spectrum | streak = White | gravity = {{val|3.78|0.09|0.16}} | density = | melt = | fusibility = | diagnostic = | solubility = Insoluble in water, weakly soluble in [HF](/source/Hydrofluoric_acid) | diaphaneity = | other = | prop1 = Mineral association | prop1text = [Olivine](/source/Olivine), [pyroxene](/source/pyroxene), [hornblende](/source/hornblende), [biotite](/source/biotite), [diamond](/source/diamond) | references = [https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Pyrope Mineralienatlas] }} thumb|Pyrope garnet in eclogite - Shibino, Ural Mountains, Russia. The mineral '''pyrope''' is a member of the [garnet](/source/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 words for ''fire'' and ''eye''. Despite being less common than most garnets, it is a widely used [gemstone](/source/gemstone) with numerous alternative names, some of which are [misnomer](/source/misnomer)s. ''Chrome pyrope'', and ''Bohemian garnet'' are two alternative names, the usage of the latter being discouraged by the [Gemological Institute of America](/source/Gemological_Institute_of_America).(Gia), Gemological. Gem Reference Guide. City: Gemological Institute of America (GIA), 1988. {{ISBN|0-87311-019-6}} Misnomers include ''Colorado ruby'', ''Arizona ruby'', ''California ruby'', ''Rocky Mountain ruby'', ''Elie Ruby'', ''Bohemian carbuncle'', and ''Cape ruby''. == Composition == 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](/source/Calcium), [Cr](/source/Chromium), [Fe](/source/Iron) and [Mn](/source/Manganese). Pyrope forms a [solid solution](/source/solid_solution) series with [almandine](/source/almandine) and [spessartine](/source/spessartine), which are collectively known as the ''[pyralspite](/source/Garnet)'' garnets ('''pyr'''ope, '''al'''mandine, '''sp'''essartine). 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](/source/rhodolite) is a garnet of ~70% pyrope composition. == Distribution == The origin of most pyrope is in [ultramafic](/source/ultramafic) rocks, typically [peridotite](/source/peridotite) from the [Earth's mantle](/source/Earth's_mantle): these mantle-derived peridotites can be attributed both to [igneous](/source/igneous) and [metamorphic](/source/metamorphic_rock) 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 {{cvt|12|cm|in|0}} in diameter; some of that pyrope has inclusions of [coesite](/source/coesite), and some has inclusions of [enstatite](/source/enstatite) and [sapphirine](/source/sapphirine). Pyrope is common in [peridotite](/source/peridotite) xenoliths from [kimberlite](/source/kimberlite) pipes, some of which are [diamond](/source/diamond)-bearing. Pyrope found in association with diamond commonly has a Cr2O3 content of 3–8%, which imparts a distinctive violet to deep purple coloration (often with a greenish tinge) and because of this is often used as a kimberlite indicator mineral in areas where erosive activity makes pinpointing the origin of the pipe difficult. These varieties are known as ''chrome-pyrope'', or ''G9''/''G10'' garnets. == Mineral identification == thumb|left|180px|Pyrope aggregate. In hand specimens, 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 adjacent table. 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](/source/mafic) and [ultramafic](/source/ultramafic) minerals may be the best indication that the garnet you are studying is pyrope. In [petrographic](/source/Petrography) [thin section](/source/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. ==References== {{Reflist|colwidth=30em}} {{Gemstones}} Category:Magnesium minerals Category:Aluminium minerals Category:Garnet gemstones Category:Cubic minerals Category:Minerals in space group 230 --- Adapted from the Wikipedia article [Pyrope](https://en.wikipedia.org/wiki/Pyrope) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Pyrope?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.