Mineraller ve özellikleri Opal General Opal Information Chemical Formula: SiO2·n(H2O) Composition: Molecular Weight = 87.11 gm Silicon 32.24 % Si 68.98 % SiO 2 Hydrogen 3.47 % H 31.02 % H 2 O Oxygen 64.29 % O ______ ______ 100.00 % 100.00 % = TOTAL OXIDE Empirical Formula: SiO 2·1.5(H 2O) Environment: Sedimentary and secondary from the alteration of high silica igneous extrusive rocks. IMA Status: Valid Species (Pre-IMA) Locality: World wide occurrences. Link to MinDat.org Location Data. Name Origin: From the Old Indian upala - "precious stone." Synonym: Fire Opal - red Hyalite - glassy Hydrophane - porous Prase - green Precious opal - opalescent Opal Crystallography Crystal System: Amorphous- No Crystals Physical Properties of Opal Cleavage: None Color: White, Yellow, Red, Brown, Blue. Density: 1.9 - 2.3, Average = 2.09 Diaphaniety: Transparent to translucent to opaque Fracture: Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz). Habits: Amorphous - No crystalline form or imitative shape., Massive - Uniformly indistinguishable crystals forming large masses., Reniform - "Kidney like" in shape (e.g.. hematite). Hardness: 5.5-6 - Knife Blade-Orthoclase Luminescence: Fluorescent, Short UV=greenish yellow, Long UV=white. Luster: Vitreous - Dull Streak: white Optical Properties of Opal Gladstone-Dale: CI meas= 0.177 (Poor) - where the CI = (1- KPDmeas/KC) KPDmeas= 0.2048,KC= 0.2489 Optical Data: Isotropic, n=1.43. Opal Classification Dana Class: (75)Tectosilicate Si Tetrahedral Frameworks (75.2)SiO2 with H2O and organics (75.2.1)Dana Group Opal SiO2·n(H2O) None Strunz Class: IV/D.01-80 IV - Oxides IV/D - Oxides with metal : oxygen = 1:2 (MO2 and related compounds) IV/D.01 - Quartz group IV/D.01-10 Quartz SiO2 P 3 121,P 3221 3 2 IV/D.01-20 Tridymite SiO2 F1 1 IV/D.01-30 Cristobalite SiO2 P 4 1212 4 2 2 IV/D.01-35 Moganite! SiO2 I2/a 2/m IV/D.01-40 Melanophlogite SiO2·n(C,H,O,S) P 4 1/nbc 4/m 2/m 2/m IV/D.01-40* Melanophlogite-beta! SiO2·n(C,H,O,S) P m3n 4/m 3 2/m IV/D.01-50 Coesite SiO2 C 2/c 2/m IV/D.01-60 Stishovite SiO2 P 4/mnm 4/m 2/m 2/m IV/D.01-70 Lechatelierite* SiO2 None IV/D.01-80 Opal SiO2·n(H2O) None