5 Some Important Crvstal Three Ways to Describe Crystal Structures Structi Why we need to know some ructure 。的小 Structural sketches of P,O, molecules Dion-stacking model: showing O= forms close packing and P (coordination polyhedron model: showing that the connection Gemstone How Can I Tell If My Diamond Is the Real Thing, Not Cubic ZrO2? Three simple way Synthetic ZrO, 2. Density test. Sapphire 3. Fog test Put the rock in front of your mouth and fog it like ou would try to fog a mirror. If it stays fogged for Diamond the heat instantaneously, so by the time you look Garnet Physical Properties of Crystals Form habit a Crystal form habit aForm: directly reflects the underlying atomic g Cleavage fracture structure(bonding, symmetry, etc ).Constant s Hardness interfacial angles a Specific gravity a Luster OHabit: the characteristic way the mineral C grows. Does not always conform to the form e.g e Streak nice perfect crystals, and depends of where grows and how made a Reaction to Acid 8 Other1 5 Some Important Crystal Structures Why we need to know some important crystal structures? Three Ways to Describe Crystal Structures Three Structural sketches of P4O10 molecules: (a)Stick-ball model：showing that the P-O chemical bond is the tetrahedral coordination and sp3 covalent bonds. (b)ion-stacking model：showing O2- forms close packing and P5+ exists in tetrahedral interstitials. (c)coordination polyhedron model: showing that the connection of the tetrahedral coordination and tetrahedron, and the octahedral interstitials is unoccupied. I Gemstone Sapphire Garnet Topaz Synthetic ZrO2 Diamond Three simple ways: 1.X-ray diffraction. 2.Density test. 3.Fog test: Put the rock in front of your mouth and fog it like you would try to fog a mirror. If it stays fogged for 2-4 seconds, it’s a fake. A real diamond disperses the heat instantaneously ，so by the time you look at it, it has already cleared up. How Can I Tell If My Diamond Is the Real Thing, Not Cubic ZrO2 ? Physical Properties of Crystals Crystal form & habit Cleavage & fracture Hardness Specific gravity Luster Color Streak Taste Reaction to Acid Other… Form & Habit Form: directly reflects the underlying atomic structure (bonding, symmetry, etc.). Constant interfacial angles. Habit: the characteristic way the mineral grows. Does not always conform to the form e.g. nice perfect crystals, and depends of where grows and how made