Piaui picotite piedra del cabo Piermatic Automatic Diamond Polishing Machine
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Sunday, 23 September 2007

Piaui. A state in Brazil and a minor producer of Diamonds. See brazil. picking table. A flat or slightly in­clined platform on which diamond-bearing ore is distributed to remove unwanted materials. It was used in the South African diamond mines until the effectiveness of grease sep­aration was discovered accidentally. It is still used in some small opera­tions.

picotite. A dark-brown, translucent to almost opaque variety of spinel; a primary mineral in the kimberlite oc­currences of South Africa. At one time it was suggested as constituting many of the dark-appearing inclu­sions in diamond, but this was not confirmed by later research.

piedra del cabo. The Spanish term for South African diamond.

Piermatic Automatic diamond Polishing Machine. The Piermatic unit was invented by Mr. M.Liebowitz, a South African civil en­gineer, and developed by the Dia­mond Trading Company in the mid-1960's and early-1970's. It is limited to the cutting of round brilliant dia­monds. Reportedly, it is best suited for processing sawn crystals (four-point Diamonds) between 0.20 carats through 0.60 carats. The unit com­pletely polishes the pavilion facets, lower and upper girdle facets, and bezel facets. The star facets, table facet and culet (if any) must be polished by the traditional (non-automated) method. The newer Piermatic II is an improved Piermatic Machine.

pierres de fantasie. A French term meaning fancy-colored Diamonds.

piggy-back diamond. An "assembled stone" composed of a flat diamond with a large culet set above, but not touching, a smaller diamond result­ing in the appearance of a much larger stone when viewed from above.