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尖晶石是鎂鋁氧化物組成的礦物，因為含有鎂、鐵、鋅、錳等等元素，它們可分為很多種，如鋁尖晶石、鐵尖晶石、鋅尖晶石、錳尖晶石、鉻尖晶石等。由于含有不同的元素，不同的尖晶石可以有不同的顏色，如鎂尖晶石在紅、藍、綠、褐或無色之間；鋅尖晶石則為暗綠色；鐵尖晶石為黑色等等。尖晶石呈堅硬的玻璃狀八面體或顆粒和塊體。它們出現在火成巖、花崗偉晶巖和變質石灰巖中。有些透明且顏色漂亮的尖晶石可作為寶石，有些作為含鐵的磁性材料。用人工的方法已經可以造出200多個尖晶石品種。

尖晶石是一族礦物，在自然界中形成于熔融的巖漿侵入到不純的灰巖或白云巖中經接觸變質作用形成的。有些出現在富鋁的基性巖漿巖中。寶石級尖晶石則主要是指鎂鋁尖晶石，是一種鎂鋁氧化物。晶體形態為八面體及八面體與菱形十二面體的聚形。顏色豐富多彩，有無色、粉紅色、紅色、紫紅色、淺紫色、藍紫色、藍色、黃色、褐色等。尖晶石的品種是依據顏色而劃分的，有紅、橘紅、藍紫、藍色尖晶石等。玻璃光澤，透明。貝殼狀斷口。淡紅色和紅色尖晶石在長、短波紫外光下發紅色熒光。

【物理性質】

  尖晶石（spinel）

  化學分子式為mgal2o4

  晶系：屬等軸晶系

  結晶習性：常呈八面體晶形，有時八面體與菱形十二面體、立方體成聚形。

  光澤：玻璃光澤至亞金剛光澤

  透明度：透明至不透明

  折光率：1.718，因含微量元素不同而改變最高可至2.000.無雙折射

  無多色性

  特殊光學效應：星光效應（四射或六射），變色效應。比較稀少

  硬度：8

密度：3.60（+0.10，-0.03）克/立方厘米

【產狀與組合】

  常產于鎂質灰巖與花崗巖類的接觸變質帶，與鎂橄欖石、透輝石等共生。基性巖、超基性巖中的尖晶石，由巖漿直接結晶形成，與輝石、橄欖石、磁鐵礦、鉻鐵礦及鉑族礦物等伴生。在富鋁貧硅的泥質巖石的熱變質帶亦可形成尖晶石，常與堇青石或斜方輝石共生。

【鑒定特征】

  八面體形態、硬度大、尖晶石律雙晶為特征。相似礦物鋯石密度較大，一軸晶；剛玉硬度更大；石榴子石硬度小于尖晶石。

【工業應用】

鎂尖晶石是鎂質耐火材料的主要結合相，也是尖晶石質耐火材料的主要物相。透明無暇、色澤美觀者可作寶石。

尖晶石耐高溫、熱膨脹系數小、熱穩定性好、抗渣性強，廣泛用于鋼鐵冶煉，水泥回轉窯及玻璃工業窯爐上

【overview】

spinel is a mineral composed of mg-al oxides, as containing magnesium, iron, zinc, manganese, etc. elements, they can be divided into many forms, such as aluminum spinel, iron spinel, zinc spinel, manganese spinel, chrome spinel and so on. due to the different elements, different spinel can have different colors, for example, magnesium spinel is between the red, blue, green, brown, and the colorless; zinc spinel is dark green and iron spinel is black, etc. spinel shows a hard glassy octahedral, granular and block. they can be founded in the igneous rock, granitic pegmatite and metamorphic limestone. some transparent and beautiful spinel can be used as precious stones and some used as an iron-containing magnetic material. now people have could produce more than 200 varieties of spinel.

spinel is a family mineral, formed by contact metamorphism in the molten magma when this magma intrusting into the impure limestone or dolomite. some appear in the al-rich basite magmatic rocks. gem-quality spinel mainly refers to mg-al spinel, an mg-al oxide. its form is the octahedron and the aggregation of octahedron and rhombic dodecahedron. they have varied colors, colorless, pink, red, purple, light purple, deep blue, blue, yellow, and brown and so on. spinel is divided by its color variety; there is red, orange, blue-violet, blue spinel and so on. pink and red spinel aglow red fluorescence when in the long and short-wave uv-wave.

【physical properties】

spinel

chemical formula: mgal2o4

crystal system: isometric system

crystal features: octahedral crystal form, the aggregation of octahedron and rhombic dodecahedron

luster: vitreous luster and sub-adamantine luster

transparency: transparent and opaque

refractive index: 1.718, it changes according to the content of trace elements; maximum is 2.000; no birefringence; no polychroism

special optical effects: star effect, aventurescence and rarity

hardness: 8

density: 3.60 (+0.10, -0.03) g / cm?

【product and combination】

it usually originates in the metamorphic belt of magnesian limestone and granite and intergrowth with magnesium olivine and diopside. the spinel in the basite and ultrabasic rocks is directly crystallized by magma, associated with pyroxene, olivine, magnetite, chromite and platinum group minerals and so on.

【features identification】

octahedral shape; hardness; great corundum hardness; harder than garnet

【industrial applications】

widely used in iron and steel smelting, cement rotary kiln and glass industry furnaces

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