美麗的青金石項鍊和耳環

青金石的原文名稱為Lapis Lazuli，來自拉丁語Lapis Lazuli，在中國古代稱為璆琳、金精、瑾瑜、青黛等。佛教稱為吠努離或璧琉璃，佛教界常使用之，其工藝品稱“青金”，古稱“金碧”、“點黛”或“璧琉璃”。 

青金石早在6000年前即被中亞國家開發使用。中國則始於西漢時期，當時的名稱是“蘭赤”、“金螭”、“點黛”等。自明清以來，青金石“色相如天”，天為上，因此明清帝王重青金石。

 　　好的青金石顏色深藍純正，無裂紋、質地細膩，無方解石雜質。不含金星（黃鐵礦）或帶有很漂亮的金星均為上品。世界上著名的青金石產地有阿富汗、智利、前蘇聯和加拿大等地。但首推阿富汗。阿國所產青金石有著均勻的深藍至天藍色，極細粒的隱晶結構中夾雜微量的黃鐵礦，使其在陽光照射之下精光生輝。青金石被阿拉伯穆斯林國家呼之為“瑰寶”。

青金石手鐲

　　青金石屬架狀結構矽酸鹽中的方鈉石族礦物，化學分子式為（Na，Ca）8（AlSiO4）6 (SO4，S，Cl)2。晶質集合體呈緻密塊狀、粒狀結構。顏色為深藍色、紫藍色、天藍色、綠藍色等。如果含較多的方解石時呈條紋狀白色，含黃鐵礦時就在藍底上呈顯黃色星點，玻璃光澤和蠟狀光澤，條痕淺藍色，半透明至不透明。折射率1.50左右，摩氏硬度5-6，一般青金石玉料比重2.7-2.9。解理不發育，斷口參差狀。在長波紫外光照射下發橙色點光，在短波紫外線照射下發綠或白色螢光。濾色鏡下呈淡紅色，遇鹽酸緩慢溶解。

青金石的結構

與青金石容易混淆的有方鈉石、藍方石、藍銅礦。冒充青金石的贗品和代用品有著色碧玉、著色尖晶石、著色岫玉、料仿青金、染色大理石。

相似玉石特徵如下：

方鈉石（又稱蘇打石），呈粗晶質結構，顏色均一，硬度5.5-6，比重2.15-2.35，折射率1.483-1.487，質地不如青金石均勻，有橙色和粉紅色螢光。

藍方石，橙紅色螢光，比重2.44-2.50，折射率1.496-1.504。

藍銅礦，硬度小，為3.5-4，折射率1.73-1.83，雙折射率 : 0.108，性脆，無大的緻密塊體。

著色碧玉（又稱瑞士青金），用玉髓或碧玉等假料人工著色而成，硬度大，為6.5-7，折射率1.53-1.55，比重:2.6。

著色尖晶石（又稱著色青金），用鈷鹽人工著色而成，硬度大，為8，折射率1.71-1.73。

著色岫玉（又稱熗色青金），淺藍色，見不到黃鐵礦，油脂光澤強，硬度4.8-5.5，折射率1.56-1.57，比重2.54-2.84。

料仿青金，用玻璃仿造，由著色的深藍色硫磺或玻璃構成的，見不到黃鐵礦，玻璃光澤，貝殼狀斷口，性脆。染色大理岩，硬度小，小刀容易刻動，遇鹽酸反應明顯。

Gilson公司合成的人工青金石

青金石在選擇上以色澤均勻無裂紋，質地細膩有漂亮的金星為佳，如果黃鐵礦含量較低，在表面不出現金星也不影響品質。但是如果金星色澤發黑、發暗，或者方解石含量過多在表面形成大面積的白斑，則價值大大降低。

 Lapis Lazuli

 中譯英:林嵩暉(GIC珠寶鑑定師資格證書、GIC翡翠鑑定師證書) 

     Lapis lazuli , from Latin name “ Lapis Lazuli”, in ancient China it called as “ Qiulin” ,  ” Jinjing ”, “ Jinyu ”, “ Qingdai ” etc. (transliteration，means “beautiful jade”).  Buddhist named it as “Feinuli”, “ Biliuli ” , which ofen applicated in Buddhist activity. The workmanship also named “Qingjing”,and named “Jingbi”,”Diandai”,or “Biliuli” in ancient China. (transliteration，means “precious jade”).

    Lapis lazuli was exploited by the Middle Asian people since 6000 years ago. It was also applicated in the Western Han Dynasty of China, named “Lanchi”, “ Jingli ”,or “ Diandai”,etc. (transliteration, “precious gemstone”). Since the Ming and Qing Dynasty ,most Chinese monarches like Lapis lazuli because of its color and looks, that like heaven. Heaven is the great, so these monarches set store by it.

   Good lapis lazuli displays ultramarine and purity, no crackle, fine and smooth quality , and no obvious calcite inside. These are all good lapis no matter what contain pyrite inside or not.  There are famous lazuli producing area in Afghanistan, Chile, the former Soviet Union, and Canada ,but product from Afghanistan is the best one. Afghanistan’s product is even, from sky blue to ultramarine color. Because its small cryptocrystalline texture mixed up with minute pyrite inside , lazuli shows glittering below sunshine. Meanwhile, Lapis lazuli is the treasure of Arab Moslem country .

Physical and chemical characteristics of lapis lazuli

     Lapis lazuli belongs to sodalite group of tectosilicate mineral, molecular formula: (Na, Ca) ₈ (AlSiO4) ₆ (SO₄, S, Cl) ₂ . Crystal aggregation body appears dense lump, graininess structure with dark blue, indigo, sky blue, or turquoise color. If lazuli contains much calcite inside , it will appears stripy white.,If pyrite, it will display yellow spots in blue background.

    Characteristics: glass or wax luster, striation with Cambridge blue color, half transparency to not clear, refractive index about 1.50 . Mohs’ scale of hardness: 5-6 , ordinary lapis lazuli :S.G.2.7-2.9, cleavage: unruly , fracture :irregular,  long wave ultraviolet light : orange fluorescence , shortwave ultraviolet ray : green or white fluorescence , CCF: rosiness color ,  in hydrochloric acid : slow dissolution.

Formation and production of Lapis lazuli

      Lapis lazuli is formed by hydrothermal contact metamorphism, mostly in silicate-magnesium skarn and calcium skarn . Lazuli is mainly composed of lazulite , sodalite, haüynite, pyrite, and calcite, so that it’s a kind of semi-precious stone.

   Lapis lazuli has the “ golden spots” on the surface ,that is pyrite ,and the white cloudy material is calcite . In Egypt and Middle East ,the ancient decorations often were made of lapis lazuli , furthermore that it was a kind of saint stone in Egypt.

    Because of different ratio of components, lapis lazuli has different color and texture . Different products display different blue because of the ratio of blue mineral and white calcite. Golden spots are formed by pyrite , and white grains are formed by white calcite .  Generally , first-class lazuli noumenon displays moderate and saturated blue , and meantime is favorable to most people.

     Lapis lazuli chief produced in Afghanistan , America, Mongolia, Myanmar, Chile, Canada, Pakistan, India and Angola etc. ,but mainland China not yet found.

Lapis lazuli and simulants

    The minerals easy to cofuse with lazuli are sodalite, haüynite , azurite . The simulants and substitutes are dyed jasper (Swiss lapis) , dyed spinel , dyed Xiuyan jade, imitated lazuli, and dyed marble etc..  

The characteristics of simulants as follows:

Sodalite : rough grain structure, even color, hardness 5.5-6, S.G. 2.15-2.35, refractive index 1.483-1.487, texture is not as good as lazuli, and there are orange and carnation fluorescence.

Haüynite : salmon pink fluorescence, S.G.:2.44-2.50, refractive index 1.496-1.504.

Azurite : small hardness: 3.5-4, refractive index :1.73-1.83, DR : 0.108 , fragile, no obvious big dense lump.

Dyed jasper (Swiss lapis) : dyed chalcedony, dyed jasper etc. , hardness : 6.5-7, refractive index 1.53-1.55, S.G.:2.6.

Dyed spinel : cobalt manpower colored up, hardness: 8, refractive index 1.71-1.73.

Dyed Xiuyan jade : Cambridge blue , no obvious pyrite, strong grease luster, hardness 4.8-5.5 , refractive index 1.56-1.57, S.G.:2.54-2.84.

Imitated lazuli: glass mimic, composed of dyed ultramarine sulfur or glass, no pyrite inside, glass luster, conchoidal fracture, fragile.

Or, dyed marble , small hardness, knife easy to carve , obvious reaction in hydrochloric acid .

Valuation and purchase of lapis lazuli

     Good lapis lazuli has even color and luster ,no obvious flaw, fine and smooth texture with beautiful golden spots.  If pyrite component is low, it will not affect its quality ,and If golden spots are too dark, or calcite content too much, so as to form large white spots on the surface, then the valuation will obviously play down.