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27 Cards in this Set
- Front
- Back
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Artificial material |
Produced by human manufacture Synthetic |
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Synthetic |
Must have a natural gem counterpart Mineral of the same composition and structure |
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Stimulant |
A synthetic material used to imitate another stone or species |
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Reaction cell
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The housing that contains the metallic catalyst and thediamond feed powder. |
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The belt process |
Reaction cell placed in a die within a metal belt which isput between to anvils. Pressure applied to a certain point, heating elementscreate a temperature gradient within the cell. Carbon moves to the cooler part ofthe sell and crystalizes. |
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The BARS process |
No press needed, liquid injected into a compression barrelwhich forces the eight segments of the internal sphere together which transferthe pressure to six smaller pistons that make up an octahedral shape. Seedcrystal, carbon source material, metal solvent, 2ct. |
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Toroid process (HPHT) |
Pyrophyllite gasket creates the pressure. Temperaturescreated by passing an electrical current through the top and bottom anvils.Same effect as BELT & BARS process. |
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Cubic press |
Six anvils that provide simultaneous pressure onto all facesof a cube-shaped reaction cell. Typically smaller but similar sized reactioncells |
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Properties of HPHT synthetic diamond |
The same physical properties as natural diamonds butdistinguishable |
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Synthetic crystals |
Grow predominately as combined forms – octahedron and cube(truncated) controlled by the temperature, pressure and orientation of the seedcrystal during the synthesis process. – may show evidence of the original seed. |
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Ib syntetic diamonds |
Produced by not adding any colour to the metallic solvent. Ibdiamonds have nitrogen in the composition which in random atoms. This is toocomplex to create and diamonds create this structure over millions of yearswhereas synthetic take a week. Therefore, most are a yellow – brownish colour. |
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IIa Nitrgen getter |
For colourless synthetic, nitrogen is introduced. By addingaluminium or zirconium to the metallic solvent. Nitrogen will bond more readilywith these elements than carbon. Prevents nitrogen form displacing carbon atomsin the crystal lattice |
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IIb synthetic diamonds |
Put boron into the reaction cell with the nitrogen getter sothe boron toms replace the carbon atoms randomly throughout the crystalstructure. Blue and will conduct electricity |
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IIb & Ib synthetic diamonds |
Yellowish-green and bluish-green |
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Coloured synthetic diamonds without adding chemicals to thestructure |
Other colours can be create by treating synthetic diamonds,irradiation – green colours, irradiation and annealing (heating) Ib will createpin colours |
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Growth patterns and colour zoning |
Often will show evidence of their cubo-octahedral growtheven when faceted. Coloured synthetics, differential impurity concentrationsbetween growth sections and growth bands, shown in octahedral patterns known ashourglass zoning |
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UV fluorescence |
HPHT Ib no reaction – typical cubo-octahedral growth sectors |
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HPHT type II synthetic diamonds |
Reverse fluorescence reaction to a natural diamond. Strong to SW than LW and long phosphorescenceto SW |
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Spectra |
Diamond have absorption band of 415nm. Not present Isynthetic, tested using Diamond smart. Not reliable as type II natural diamonddo not have this line. |
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Inclusions in synthetic diamonds |
Metallicflux, dust/breadcrumb inclusions. Usually very clean |
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Magnetism |
Minute metallic solvent inclusions trapped in the diamondduring growth process means the synthetic diamond is attracted to a highpowered rare earth magnet. Older or poor quality synthetic diamonds. |
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Chemical vapour deposition CVD synthetic diamond |
Doesn’t need as high temperature and pressure as HPHTArgon, oxygen, hydrogen, methane. Vacuum to mix the gases.Forms as graphite ad diamond, the hydrogen etches away the graphite on thesurface. Cheaper than HPHT now. Can also create polycrystalline layers anddiamond coatings on various materials. |
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Properties of CVD |
Physical properties are the same as natural diamond, mayshow a higher-order strain patterns/colours when viewed between crossedpolarising filters. |
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CVD crystals |
Seed plate produces flat, wafer-like crystals. Seed crystalof natural HPHT grown or CVD grown used as a nucleation point. Carbon depositsin three directions to form cube of high purity diamond so the forms in CVD aredifferent to both natural and HPHT diamond. Can grow several on the plate thatwill be same colour and clarity. |
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Colour & diamond types |
CVD no nitrogen impurities – IIaFaint brown to dark brown colour – colourless can beproducedBrown CVD synthetics then HPHT to make colourless |
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Colour zoning |
CVD form in layers rather than more complex directions takenin HOHT growth. More noticeable with high energy UV – DiamondView.Significantly different to anything seen in natural o HPHT |
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orange fluorescence CVD |
Orange will vary in intensity. If colourless CVD nofluorescence. SWUV blue glow if phosphorescence is present. |
