WinJewel is a complete program to run a retail jewelry store. Click on "Home" above to go to our start page. This jeweler's dictionary is provided as a free service by WinJewel.

Click on the letter of the word you want:


    Pacific Cat's-eye alternative name for operculum. See Operculum and Chinese cat's eye.

    Padparadschah a name applied to a peculiar orange-pink variety of natural gem corundum, and also used, with variations in spelling, for synthetic corundum of similar colour.

    Pagoda stone a type of translucent agate which when cut shows markings resembling a Burmese pagoda, in opaque white bands which appear to float in the colourless translucent body material. Also used for agalmatolite.

    Painite Calcium boro-silico aluminate. R.I. 1-79 --- 1-82; S.G. 4-01; H. 7.5; Hexagonal; Burma.

    Painted stones a fraudulent method used to improve the colour appearance of yellowish or brownish diamonds by applying a film of blue colour to the base facets. The best method of detecting such a fraud is to soak the stone in spirits or to boil the stone in sulphuric acid. Pale colour emeralds and rubies have had their colour enhanced by coating the back facets with coloured varnish or dye. The detection method suggested for diamond will also apply to these stones.

    Palladium S.G. 114; a metal of the Platinum group, similar in colour to platinum and used, owing to lower cost, for jewelry and the arts instead of platinum.

    Parian marble a pure white marble.

    Parti-coloration the effect seen in crystals which are coloured dierently in different parts. Stones cut from such crystals will show two or three colours, such as red one end with green the other, and, maybe, colourless in centre. Such stones are termed Parti-coloured. Parti-coloration is often shown in corundum and tourmaline.

    Parting (or False cleavage) a direction of weakness in certain crystals (e.g., corundum) due to lamellar twinning.

    Paste name given to the glass used for imitation gemstones. See also Strass.

    Pavilion facets the long five-sided facets on the pavilion, or base, of a brilliant-cut stone.

    Pearl a concretion consisting of concentric layers of an organic material (conchiolin) and crystalline calcium carbonate in the form of aragonite arranged radially around a small body as nucleus. S.G. 2 65 to 2 78; Localities, Persian Gulf, Ceylon (Gulf of Manar), north-west coast of Australia, Philippine Islands, coast of Venezuela, Gulf of Mexico, Pacific Ocean Islands, rivers of U.S.A., Europe and China.

    1 Baroque; a pearl of irregular shape.
    2 Black; a pearl of bronze or gunmetal tint from the Gulf of Mexico and certain other localities.
    3 Blister; pearl formed attached to the shell of the mollusc.
    4 Blue; natural pearl in which the nucleus is mud, clay or organic material.
    5 Cultured; a pearl in which the nucleus (of mother-ofpearl) had been artificially inserted in the oyster.
    6 Freshwater or Mussel; a pearl found in the Pearl Mussel (Unio margaritifera) in rivers of Scotland, Europe and U.S.A.
    7 Pink; obtained from a univalve shellfish, the Indian conch or "Abalone". A non-nacreous pearl.

    Pearl sac the term applied to the bag of epithelial cells (part of the mantle) which surrounds the pearl in the flesh of the oyster. The pearl sac is an essential condition for the formation of cyst pearls, either natural or cultured.

    Pearls, Calculation of prices; see Chart.

    Pectolite R.I. 1-59 --- 1-63; S.G. 2-74 to 2-88; H. 5; Monoclinic (massive); Greyish white; U.S.A., Italy and Scotland.

    Pegmatite a coarse-grained quartz-feldspar igneous rock.

    Pendeloque a style of cutting. A drop-shaped stone. See Styles of cutting, Chart 18 l.

    Pennyweight, Pwt or Dwt 1 penny wt.= 5% of an ounce "Avd" 20 to the ounce. 1/20thof ounce, 24 grains, 0.05 ounces, 0.0648 grams.

    Periclase a magnesium oxide mineral now produced synthetically under the name "lavernite". Cubic. H. - 5; S.G.=3 55 to 3 60 and R.I. = 1 73.

    Peridot R.I. 1 654-1 689; S.G. 3 34; H. 61 to 7; Rhombic; Colours, oil-green, brown; Localities, Red Sea, Burma, Ceylon, U.S.A. and Norway. (Mineralogical name of the species is Olivine).

    Periostracum the name given to the outer dark horny layer of conchiolin forming the outside of the shell of the oyster.

    Peristerite a variety of albite feldspar showing a bluish opalescence somewhat like labradorite.

    Petalite R.I. 1-50 --- 1-516; S.G. 2-39 to 2-46; H. 6; Monoclinic (crystals rare, material usually massive); Colourless or white; Sweden and Maine, U.S.A.

    Petroleum a hydrocarbon liquid having a value as an immersion liquid in certain refractive index tests. R.I.= 1-45.

    Petrology the study of the mineral constitution of rocks and their mode of formation.

    Petrological microscope see Microscope.

    Phantom Crystals see Ghost crystals.

    Phenakite R.I. 1 651-1 666 to 1 653-1 668; S.G. 295 to 297; H. 71 to 8; Trigonal; Colours, colourless, yellowish and pale pink; Localities, Ural Mountains (Russia) and North and South America.

    Phenyldi-iodearsine a highly refractive liquid (R.I. 185) used for making optical contact between stone and dense glass of refractometer, and as an immersion fluid. It is poisonous and has a blistering action on the skin.

    Phosphorescence is the continuance of fluorescent light after the exciting radiations causing the luminescence have ceased. See also Fluorescence.

    Phosphoroscope an apparatus for measuring the duration of phosphorescence.

    Photomicrograph a photograph of the view of a subject as seen through a microscope. A special camera is used which fits on the tube of the microscope in place of the eyepiece, or over the eyepiece.

    Piezo-electricity the property certain crystals (notably quartz and tourmaline) possess of inducing a charge of electricity in themselves when pressure is applied along certain directions in the crystal.

    Pil - Treated diamonds Diamonds coloured by bombardment with neutrons from an atomic pile (atomic reactor). As in cyclotroned diamonds the colours are green and after heat treatment brown. These stones are not radio-active and are coloured throughout.

    Pinacoidal face a crystal face that is parallel to two of the crystal axes.

    "Pink moonstone" a name erroneously applied to the opalescent pink variety of scapolite.

    Pique the term applied to diamonds which have inclusions obvious to the naked eye.

    Pistacite see Epidote.

    Planes of symmetry those planes in an ideally developed crystal which divide it in such a way that one side of each plane is the mirror image of the other.

    Plasma see Chalcedony.

    Plastics an omnibus term used for a number of synthetic substances, generally resin-like, which can be moulded by heat and pressure. See Chart 176.

    Platinum S.G. 21-5; a hard and ductile grayish-white metal used for mounting gemstones, particularly diamonds. The metal has a high melting point (1755 C.) hence is employed where heat resistance is required.

    Play of colour iridescence due to interference of light impinging on thin films having a different refractivity to the surrounding mass. Seen in precious opal, labradorite, etc.

    Pleochroism the optical effect of gem stones of having different colors depending on which optic axis that the viewer is looking at.

    Pleonaste see Spinel.

    Point the term used in describing the weight of diamonds or other gems under one carat. The "point" is 0.01 carat so that a fifty point diamond weighs 0.50 carat, or half a carat. A seventy point stone weighs 0.70 carat.

    Polariscope an instrument consisting of two units for the production of plane polarised light arranged with a rotating stage between them. The lower unit (the unit may be a Nicol prism, an Ahrens prism, a "Polaroid" disc or may be a mirror arranged at the requisite angle) is termed the "polariser" and the similar unit above the stage the "analyser". The polariser, and sometimes the analyser, are capable of being rotated at right angles to the optical axis of the insku. meet. The polariscope is used to examine substances in parallel and convergent light. All petrological microscopes are fitted with the device.

    Polarised light light which is vibrating in one plane only, whereas with ordinary light the plane in which the vibrations may take place are infinite in number. In all rays of light, polarised or unpolarised, the vibrations are at right angles to the directions the light is travelling. Doubly refracting crystals not only resolve the light that passes through them into two rays but completely polarise them in planes at right angles to one another.

    Polaroid sheets of plastic material containing ultra-microscopic crystals of quinine iodosulphate which have the property of transmitting only one polarised ray, the other being almost entirely absorbed by the crystals. May be used in place of the more expensive Nicol prisms.

    Pollucite R.I. 1-51; S.G. 2-86; H. 6.5; Cubic; Colourless; Localities U.S.A. and Isle of Elba.

    Polymorphism the term used where minerals which have the same chemical composition crystallise in different forms, e.g., Rutile; Anatase and Brookite all correspond to the formula TiO2 but each appears in different crystal form. See Dimorphism.

    Polystyrene a plastic. A polymerisation product of vinyl benzene. R.I. 1-59 to 1-67; S.G. 1-05; H. 2.5. Dissolves in hydrocarbon liquids, e.g., benzene, bromoform, etc.

    Polysynthetic twins contact twin crystals producing a number of very thin plates (laminate or lamellae). Each adjacent plate is in reverse order in alternate plates they are in the same order. Sometimes called repeated or lamellar twinning. Weakness along the cGntact planes gives rise to "Parting" or "False cleavage".

    Porcelain a type of fine earthenware (china) made from china-clay (kaolin) sometimes used for making opaque imitation stones, such as turquoise. S.G. 2 1 to 2 5.

    Porphyries types of igneous rocks which show comparatively large and well-formed crystals embedded in a fine "rained ground mass. Red and green coloured porphyries were much used in Greco-Roman times.

    Potch opal Miners term for opal which does not show the play of colour seen in precious opal.

    Powder, Diamond see Diamond Powder.

    Prase green massive quartz.

    Prasiolite the name given to the green quartz due to the heat treatment of amethyst.

    Precious stones A term usually confined to such stones as the diamond, ruby, sapphire, emerald, and perhaps black opal. It is an older term with little effective meaning because many other stones are more expensive than these, especially if these are of low quality and the other stone if of fine quality.

    Prehnite R.I. 1-62 --- 1-65; S.G. 2-80 to 2-95; H. 6 to 7; Rhombic; Colour, green (may resemble jade) and brown; Localities, France, U.S.A. and Australia.

    Pressed amber amber which has been made up of small pieces welded together by hydraulic pressure under heat; a true reconstruction. Alternatively called Ambroid.

    Princess Cut a square cut of diamond that uses back facets that are more like a brillant cut diamond; an old and discontinued name for the profile cut which is used for diamonds and other stones.

    Profile cut a style of cutting for diamond (and has been used for other stones) in which flat slices of diamond are cut with grooves on the reverse side. Said to give economy of material and facilitates setting by the fact that all stones are cut to definite sizes. Previously known as the Princess cut.

    Proustite R.I. 2-7 --- 3-0; S.G. 5-57 to 5-64; H. 2.5; Trigonal; Red (darkens on exposure to light); Central Europe, Chile, France, Mexico and U.S.A.

    Pseudomorph the term used to describe a mineral which has been altered from another, but in which the original form has been retained.

    Pseudophite a hydrated silicate of aluminium and magnesium; R.I. 1-576 - 1-579; S.G. 2-6 to 2-85; H. 2.5; Colour, green; Localities, Switzerland, Italy, Styria (Austria) and Scandinavia. Known also as "Styrian Jade".

    Psilomelane a manganese mineral which when cut and polished resembles hematite and has been used similarly.

    Pumice powder a highly cellular, glassy volcanic rock or lava used as a polishing agent.

    Pumicite or Volcanic dust a natural glass or silicate atomised by volcanic explosions. The material is similar in composition to pumice powder and like this latter material is used for polishing purposes.

    Punamu the Maori name for the jade from New Zealand. See Nephrite.

    Purple gold may be obtained by the use of aluminium as an alloy. This alloy, however, is too brittle for use in jewelry.

    Putty powder a polishing medium consisting of tin oxide (about 85 to 90%) with the remainder lead oxides.

    Pyknometer see Specific Gravity Bottle.

    Pyralspite series the name applied to the isomorphous series of garnets which contain the pyrope/almandine/spessartite group.

    Pyrite (pyrites) S.G. 4-84 to 5-10; H. 6..5; Cubic; Colour brass-yellow. Pyrite is the "Marcasite" of jewelry.

    Pyro-electricity the property of certain crystals (particularly tourmaline) of acquiring an electric charge when they are heated.

    Pyrope see Garnet.

    Pyrophyllite R.I. mean 1-58; S.G. 2-8; H. 1.5; White, grey or greenish and resembles soapstone. The crystallization is orthorhombic but the mineral is always massive. Russia, Brazil, U.S.A. and South Africa where the grey material has been marketed under the name "wonderstone".

    Pyroxene The name applied to a group of minerals whose physical and optical characters serve to link them together. They are closely analogous chemically to the amphibole group (which see). The gem members of the pyroxene minerals are; enstatite, diopside, jadeite and spodumene.