A Granada (do latim granatus, um grão) é o nome geral dos membros de um grupo de minerais com habitus cristalino constituído por
dodecaedros e trapezoedros. São nesosilicatos de fórmula geral, A3B2(SiO4)3. As diversas variedades de granada
podem incorporar diversos elementos químicos na sua estrutura, principalmente
cálcio, magnésio, alumínio, ferro2+, ferro3+, cromo, manganês e titânio. As
granadas não apresentam clivagem, mas mostram partição dodecaédrica. A fratura
é concoidal a desigual; algumas
variedades são muito resistentes e são valiosas para finalidades abrasivas. A
dureza das granadas encontra-se no intervalo 6,5-7,5 e a densidade (peso
específico) está entre 3,1 e 4,3. O brilho varia entre vítreo e resinoso,
podendo ainda ser transparentes ou opacas, conforme a presença ou ausência de
inclusões. As granadas podem apresentar as seguintes cores: vermelho, amarelo,
marrom, preto, verde, ou incolor.
Os membros do grupo da granada subdividem-se através da sua
variabilidade química.
Pingente em uvarovite, uma granada brilhante-verde rara. A dimensão é 2 cm (0,8
polegadas).
Um agregado de cristais de granada.
Amostra de rocha portadora de granada.
Piropo
Piropo, ou Rubi do Cabo, é uma granada de cor vermelho-sangue,
devido a seu conteúdo de ferro e cromo. A sua fórmula é Mg3Al2(SiO4)3. O
magnésio pode ser substituído em parte por cálcio e/ou ferro ferroso (Fe2+).
O piropo raramente possui inclusões, mas, quando presentes, estas
se encontram em forma de cristais arredondados ou apresentam contorno
irregular. Como todas as granadas, o piropo não possui clivagem, e a fratura é
de subconcoide a irregular.
O piropo é encontrado em rocha vulcânica e depósitos aluviais e
pode, juntamente com outros minerais, indicar a presença de rochas portadoras
de diamantes. As localizações de jazidas incluem Arizona, África do Sul,
Argentina, Austrália, Brasil, Myanmar, Escócia, Suíça e Tanzânia.
Os exemplares transparentes são usados como gemas. Uma variedade
importante de piropo - a rodolite, do grego a rosa - é originária do condado de Macon na Carolina do
Norte, é caracterizada pela cor violeta-vermelha e por constituir uma solução
sólida de 2:1 entre piropo e almandina.
A palavra piropo deriva do grego pyropos, significando flamejante.
Os piropos suíço e sul-africano são pedras de vermelho mais claro do que as
pedras da Boémia, onde se utiliza o piropo na joalheria há mais de quinhentos
anos.
Grossularite
Grossularite ou grossulária é uma granada de cálcio-alumínio com a fórmula Ca3Al2(SiO4)3,
embora o cálcio pode em parte ser substituído por ferro ferroso (Fe2+) e o
alumínio por ferro férrico (Fe3+). As cores mais comuns deste mineral são
verde, canela, marrom, vermelho, e amarelo. A grossularite é um mineral típico de
metamorfismo de contacto de calcários, onde se encontra associada a vesuvianite, diópsido, wollastonite e wernerite. Grossularite é um termo derivado da
botânica.
Almandite
Almandite, almandina ou carbúnculo é uma granada do ferro-alumínio com a
fórmula Fe3Al2(SiO4)3. As variedades transparentes podem ter bastante valor
enquanto pedras preciosas. A almandite é um mineral comum em rochas metamórficas como o micaxisto, onde
ocorre associado a estaurolite, distena, andaluzite, entre outros.
Espessartite
Espessartite ou Spessartita é uma granada de manganês e alumínio de fórmula Mn3Al2(SiO4)3. O
nome é derivado da cidade de Spessart na Baviera. Esta variedade pode apresentar cores variadas, de
acordo com o tipo e quantidade de impurezas. As mais famosas são as espessartites laranja de Madagascar e os
exemplares violeta-vermelhos que ocorrem em riólitos do Colorado e Maine.
Uvarovite
Uvarovite ou Uvarovita é uma granada de cálcio e cromo de fórmula Ca3Cr2(SiO4)3. Dentro
do grupo da granadas, é a variedade mais rara, surgindo em pequenos cristais de
cor verde associados a cromita e serpentina.
A atraente e brilhante cor verde da uvarovite se deve à presença de
cromo. Os cristais são muito frágeis, com fratura de subconcoide a irregular.
A uvarovite ocorre em rochas de serpentina. Os melhores cristais são
encontrados nos Urais, na Rússia, em torno de cavidades ou fissuras na rocha.
Outras fontes são a Finlândia, a Turquia e a Itália.
Andradite
Andradite ou Andradita é uma granada de cálcio e ferro de fórmula Ca3Fe2(SiO4)3, embora
sejam comuns substituições catiónicas importantes. As cores dependem destas variações e podem ser
vermelho, amarelo, marrom, verde ou preto. As variedades reconhecidas são topazolite (amarelo ou verde), demantoide (verde) e melantite (preto). A andradite pode ser encontrada em
rochas ígneas de profundidade, como os sienitos, e em rochas metamórficas como os xistos e calcários. Seu nome
homenageia o mineralogista brasileiro José Bonifácio de Andrada e Silva, mais
conhecido por sua atuação na história política do Brasil, que lhe valeu o
cognome de Patriarca da Independência.
Meet Natural Stone- Granada
The Granada ( the granatus Latin, a grain ) is the general name of the members of a group of minerals with crystalline habitus consists of dodecahedra and trapezoedros . Nesosilicatos are of the general formula , A3b2 ( SiO4 ) 3. The different varieties of garnet can incorporate various chemical elements in its structure , especially calcium , magnesium, aluminum , ferro2 + + ferro3 , chromium, manganese and titanium . Garnets do not show cleavage , but show Dodecahedral partition . The fracture is conchoidal to uneven , some varieties are very hardy and are valuable for abrasive purposes . The hardness of the grenade is in the range 6.5-7.5 and the density ( specific gravity ) is between 3.1 and 4.3 . The brightness varies from vitreous and resinous , and may be transparent or opaque , depending on the presence or absence of inclusions. Garnets may have the following colors : red, yellow, brown , black, green , or colorless .The members of the garnet group are subdivided by their chemical variability.Pendant uvarovite , a rare bright - green garnet . The size is 2 cm ( 0.8 inches).An aggregate of garnet crystals .Rock sample carrier grenade.
Pyrope
Pyrope , or Ruby Cape , is a garnet -red blood because of its content of iron and chromium . Its formula is Mg3Al2 ( SiO4 ) 3 . The magnesium can be partly replaced by calcium and / or ferrous iron ( Fe2 +).The pyrope rarely has inclusions , but , when present , these are in the form of rounded or irregular contour feature crystals . Like all grenades , the pyrope has no cleavage , and the fracture is irregular subconcoide .The pyrope is found in volcanic rock and alluvial deposits and may , along with other minerals , indicate the presence of diamond bearing rocks . The locations of quarries include Arizona , South Africa , Argentina , Australia , Brazil , Myanmar , Scotland , Switzerland and Tanzania .Transparent specimens are used as gems . An important variety of pyrope - the Rodolite , greek rose - is originally from Macon County in North Carolina , is characterized by the violet - red color and form a solid solution between pyrope and almandine 2:1 .The word derives from the pyrope pyropos Greek, meaning flaming . The Swiss and South African flirting red stones are lighter than the rocks of Bohemia , which uses the pyrope in jewelry for over five hundred years.
Grossularite
Grossularite or grossular is a calcium - aluminum garnet with Ca3Al2 ( SiO 4 ) 3 formulation, although calcium may be partially replaced by ferrous iron ( Fe2 +) to ferric iron and aluminum ( Fe3 +). The most common colors of this mineral are green, cinnamon , brown, red , and yellow . The grossularite is a typical mineral of contact metamorphism of limestone , which is associated with vesuvianite , diopside , wollastonite and wernerite . Grossularite is a term derived from botany.
Almandite
Almandite , almandine or carbuncle is an iron - aluminum garnet with Fe3Al2 ( SiO 4 ) 3 formula. The transparent varieties may have enough value as gemstones . The almandite is a common mineral in metamorphic rocks such as mica , which occurs in association with staurolite , kyanite , andalusite , among others .
Espessartite
Espessartite or Spessartita is a grenade manganese and aluminum Mn3Al2 formula ( SiO4 ) 3 . The city name is derived from Spessart in Bavaria . This variety may exhibit different colors according to the type and amount of impurities. The most famous are the orange espessartites Madagascar and copies violet - red that occur in rhyolites in Colorado and Maine .
Uvarovite
Uvarovite or uvarovita is a grenade calcium and chromium Ca3Cr2 of formula ( SiO4 ) 3 . Within the group grenades , is the rarest variety , appearing in small green crystals associated with chromite and serpentine .The eye-catching and bright green color uvarovite due to the presence of chromium . The crystals are very fragile , with subconcoide irregular fracture.The uvarovite occurs in serpentine rocks . The best crystals are found in the Urals, Russia, around cavities or fissures in the rock . Other sources are Finland , Turkey and Italy .
Andradite
Andradite and andradite garnet is a calcium and iron Ca3Fe2 formula ( SiO4 ) 3 , although common major cationic substitutions . The colors depend on these variations and can be red, yellow , brown, green or black . The recognized varieties are topazolite (yellow or green ) , demantoid ( green) and melantite ( black) . The andradite can be found in igneous rocks deep, as syenite , and metamorphic rocks such as shales and limestones . Its name honors the Brazilian Mineralogist Jose Bonifacio de Andrada e Silva , best known for his role in the political history of Brazil , which earned him the nickname Patriarch of Independence .
Meet Natural Stone- Granada
The Granada ( the granatus Latin, a grain ) is the general name of the members of a group of minerals with crystalline habitus consists of dodecahedra and trapezoedros . Nesosilicatos are of the general formula , A3b2 ( SiO4 ) 3. The different varieties of garnet can incorporate various chemical elements in its structure , especially calcium , magnesium, aluminum , ferro2 + + ferro3 , chromium, manganese and titanium . Garnets do not show cleavage , but show Dodecahedral partition . The fracture is conchoidal to uneven , some varieties are very hardy and are valuable for abrasive purposes . The hardness of the grenade is in the range 6.5-7.5 and the density ( specific gravity ) is between 3.1 and 4.3 . The brightness varies from vitreous and resinous , and may be transparent or opaque , depending on the presence or absence of inclusions. Garnets may have the following colors : red, yellow, brown , black, green , or colorless .The members of the garnet group are subdivided by their chemical variability.Pendant uvarovite , a rare bright - green garnet . The size is 2 cm ( 0.8 inches).An aggregate of garnet crystals .Rock sample carrier grenade.
Pyrope
Pyrope , or Ruby Cape , is a garnet -red blood because of its content of iron and chromium . Its formula is Mg3Al2 ( SiO4 ) 3 . The magnesium can be partly replaced by calcium and / or ferrous iron ( Fe2 +).The pyrope rarely has inclusions , but , when present , these are in the form of rounded or irregular contour feature crystals . Like all grenades , the pyrope has no cleavage , and the fracture is irregular subconcoide .The pyrope is found in volcanic rock and alluvial deposits and may , along with other minerals , indicate the presence of diamond bearing rocks . The locations of quarries include Arizona , South Africa , Argentina , Australia , Brazil , Myanmar , Scotland , Switzerland and Tanzania .Transparent specimens are used as gems . An important variety of pyrope - the Rodolite , greek rose - is originally from Macon County in North Carolina , is characterized by the violet - red color and form a solid solution between pyrope and almandine 2:1 .The word derives from the pyrope pyropos Greek, meaning flaming . The Swiss and South African flirting red stones are lighter than the rocks of Bohemia , which uses the pyrope in jewelry for over five hundred years.
Grossularite
Grossularite or grossular is a calcium - aluminum garnet with Ca3Al2 ( SiO 4 ) 3 formulation, although calcium may be partially replaced by ferrous iron ( Fe2 +) to ferric iron and aluminum ( Fe3 +). The most common colors of this mineral are green, cinnamon , brown, red , and yellow . The grossularite is a typical mineral of contact metamorphism of limestone , which is associated with vesuvianite , diopside , wollastonite and wernerite . Grossularite is a term derived from botany.
Almandite
Almandite , almandine or carbuncle is an iron - aluminum garnet with Fe3Al2 ( SiO 4 ) 3 formula. The transparent varieties may have enough value as gemstones . The almandite is a common mineral in metamorphic rocks such as mica , which occurs in association with staurolite , kyanite , andalusite , among others .
Espessartite
Espessartite or Spessartita is a grenade manganese and aluminum Mn3Al2 formula ( SiO4 ) 3 . The city name is derived from Spessart in Bavaria . This variety may exhibit different colors according to the type and amount of impurities. The most famous are the orange espessartites Madagascar and copies violet - red that occur in rhyolites in Colorado and Maine .
Uvarovite
Uvarovite or uvarovita is a grenade calcium and chromium Ca3Cr2 of formula ( SiO4 ) 3 . Within the group grenades , is the rarest variety , appearing in small green crystals associated with chromite and serpentine .The eye-catching and bright green color uvarovite due to the presence of chromium . The crystals are very fragile , with subconcoide irregular fracture.The uvarovite occurs in serpentine rocks . The best crystals are found in the Urals, Russia, around cavities or fissures in the rock . Other sources are Finland , Turkey and Italy .
Andradite
Andradite and andradite garnet is a calcium and iron Ca3Fe2 formula ( SiO4 ) 3 , although common major cationic substitutions . The colors depend on these variations and can be red, yellow , brown, green or black . The recognized varieties are topazolite (yellow or green ) , demantoid ( green) and melantite ( black) . The andradite can be found in igneous rocks deep, as syenite , and metamorphic rocks such as shales and limestones . Its name honors the Brazilian Mineralogist Jose Bonifacio de Andrada e Silva , best known for his role in the political history of Brazil , which earned him the nickname Patriarch of Independence .
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