PIETRA ALBERO :

Italian name for mocha stone.

PIETRA de HIJADA :

Italian name for nephrite.

PIGEON BLOOD RUBY :

Designates the most desired nuance of red colour for a ruby (= a very fine dark, very luminous red ) .

PILARITE :

Variety of chrysocolla containing Aluminium .

PIMELITE :

Variety of garnierite.

PINGO de AGOA :

Name given by the Brazilians to a colourless topaz (French : topaze goutte d’eau).

PINGOO :

Burmese Term designating rubies with lots of silk .

PINGOO-CHOO :

Burmese Term designating a better quality of star ruby .

PINITE :

Variety of amorphous and opaque cordierite of grey or brown colour, or mineral resulting from a decomposition of cordierite and belonging to the group of the micas (Dana ).

Variety of agalmatolite or variety rich in silica of this mineral ( Smith ) .

PINK TOPAZ :

Most often a pink topaz obtained by heat-treatment of the yellow or brown topaz variety.

PINK MOONSTONE :

Prohibited Appellation for a scapolite or a pink girasol .

PIN POINT :

Variety of blue or green opal with small dots of golden colour (giving the impression of a sparkling fire).

PINTAS OPAL :

Mexican name for opals showing a particularly brilliant spectrum of colours.

PIOTINE :

Variety of saponite.

PIRUZE or FIRUZE:

Persian name for turquoise.

PISSITE :

Synonym for semi-opal.

PISSOPHANE :

Opal of low quality and treated, or hydrophane impregnated with wax .

PISTACITE :

Synonym of epidote.

Etym. : from its pistachio green ( or brownish-green ) colour .

PISTAZITE :

Synonym for pistacite.

PIT AMBER :

English Name given to amber obtained through mining activity, contrasting with amber of marine origin .

PITCH COAL :

(English) Synonym for jet.

PITCH GARNET:

Andradite of a very dark yellow colour.

PITCH OPAL :

Common yellowish or brownish opal with a rather dull lustre .

PITCH STONE :

Obsidian of grey, yellow, red or brown colour, containing more water and of a hardness superior to the greater part of the other obsidian varieties ( D. 5.5 to 6 ) .

PI YU :

Chinese Name for a variety of nephrite of a vegetable green colour equally used for designating a jadeite of the same colour .

PLAGIOCLASE :

Group of feldspaths comprising albite, oligoclase and labradorite .

PLASMA :

Crypto-crystalline opaque to semi-translucent quartz of green to green dark colour

Hardness : 7

Density : 2.65

R.I. : 1.54 to 1.55

PLASTIC :

Artificial or synthetic material, transparent to opaque serving sometimes to imitate precious stones, but equally serving to imitate resinous materials such as amber.

Following here below the different principal plastic materials:

Celluloïds : (nitrate with cellulose)

Hardness : 1.5

Density : 1.27 to 1.81 (generally 1.36 to 1.42)

R.I. : 1.495 to 1.51

Acetate with cellulose :

Hardness : 1.5

Density : 1.27 to 1.80 (generally 1.29 to 1.42)

R.I. : 1.470 to 1.505

Vinyl : (polyvinyl or chlorovinyl acetates)

Density : 1.15 to 1.35

Polystyrene : (polystyrol – vinyl benzene)

Hardness : 2 to 2.5

Density : 1.05 to 1.07

R.I. : 1.59 to 1.67

Perspex : (synthetic resin, methylmethacrylate resin also called acrylic resin or Diakon, or Plexiglas )

Hardness : 2 to 2.5

Density : 1.18 to 1.19

R.I. : 1.49 to 1.52

Bakelite : ( phenol and formaldehyde , called Catalin for the imitations of coloured stones )

Hardness : 2 to 2.5

Density : 1.25 to 2.00 ( generally 1.25 to 1.30 )

R.I. : 1.54 to 1.70 ( generally 1.62 to 1.66 )

Pollopas : ( formaldehyde, also called amino resin, and commercialised under the names of Beetle and Scarab )

Hardness : 2 to 2.5

Density : 1.42 to 1.60

R.I. : 1.55 to 1.63 ( generally 1.50 )

Caseine : ( caseine and milk, hardened with formaldehyde , equally known under the names of galalithe, lactoïd, erinoïd )

Hardness : 2 to 2.5

Density : 1.32 to 1.39 ( generally 1.33 )

R.I. : 1.54 to 1.56

PLEONASTE :

Synonym for ceylonite.

Variety of very dark green almost black coloured spinel

(MgFe)A1₂0₃

Physical and optical properties :

-     - colour : black, greenish black

-     - Hardness : 7.5 to 8

-     - Density : 3.50 to 3.60 ( may go up to 4.06 )

-          - System : cubic

-           

PLUMBOFERRITE :

Spinel containing Fe, Mn , Pb

PLUMBOMALACHITE :

Malachite containing Pb

POLIOPYRITE :

Synonym for marcassite.

POLKA-DOT AGATE :

Local name for a chalcedony, generally colourless , having yellow, red or brown , circular spots and found in Oregon, USA.

POLLUCITE :

Rare mineral exploited for its high Caesium content.

H₂Cs₄A1₄(SiO₃)₉     

Physical and optical properties :

-     - colour : colourless, white pale, blue

-     - Transparency : transparent to translucent

-     - Hardness : 6.5

-     -Density : 2.86 to 2.94

-     - R.I. : 1.518 to 1.526 (+0.024)

-     - Dispersion : 0.007 to 0.012

-          - System : cubic

-           

POLLUX :

Synonym for pollucite .

POLYADELPHITE :

Variety of aplome of brown opaque colour .

POLYBERN :

Imitation of amber composed of polymer and small fragments of natural amber .

POLYCHROITE :

Alteration of cordierite.

POLYKRASILITH :

Synonym for zircon.

POLYPHANT :

Diabase serpentine from Cornwall , England .

POMEGRANATE RUBY :

Prohibited Appellation, employed in India for a red spinel .

PONTIC CHRYSELECTRI :

Name found with Plinius. Synonym for citrine .

POPO :

West African Term for a green jasper .

POPPY STONE :

Local Name for an orbicular red jasper from California .

PORCELLANITE :

Variety for serpentine or name given to a red or green jasper with porcelain aspect  .

PORCELLOPHITE :

Name given to a skind of serpentine, probably belonging to the group of the antigorites .

POTSTONE :

English Name for steatite .

PRAMNOIN :

A very dark jasper .

PRASE :

Variety of Quartz, opaque massif aggregate of leek green colour containing generally actinolite needles .

PRASE OPAL :

Variety of common opal of green colour.

PRASEM :

Synonym for prase .

PRASEOLITE :

Alteration of cordierite ; has a vitreous lustre .

PRASIOLITE :

Amethyst or yellowish Quartz (mainly from the Montezuma mine, Minas Gerais,

Brazil and from Arizona) of which one has changed the colour into leek-green by heat-treatment at 500°C.

PRASER :

Synonym for chrysoprase.

PRASIUS :

Synonym for prase.

PRASOPAL :

Common Opal of apple green colour colour due to chromium .

PREHNITE :
Etym. dedicated to colonel Von Prehn (1790) who discovered it at the Cape of Good Hope

It is an aggregate

H₂Ca₂A1₂(SiO₄)₃    

Physical and optical properties :

-          - Colour : asperagus green, oily green, apple green, whitish green, white or yellowish, pale yellow

-            to yellowish, greyish green, brownish

-     - Transparency : transparent to translucent

-     - Hardness : 6 to 7

-     - Density : 2.80 to 2.95

-     - R.I. : 1.618 (+0.012 –0.007) – 1.648(+0.021-0.016)

-     - Birefringence : 0.030 (to 0.039)

-     - Dispersion : none

-     - Biaxial positive

-     - System : orthorhombic

PREHNITOIDE :

Variety of impure prehnite or a variety of scapolite.

PRENIA :

Synonym for prehnite.

PRINCESS BLUE :

Commercial English Name for a sodalite of nice blue colour from Bancorft, Ontario, Canada .

PRISMATINE :

Variety of kornerupine.

PROLECTITE :

Variety of Chondrodite. 

PSEUDO-ANDALOUSITE :

Variety for disthene (Kyanite).

PSEUDO-CHRYSOLITE :

Prohibited Appellation for a moldavite.

PSEUDO-DIAMOND :

Prohibited Appellation for a colourless Quartz.

PSEUDO-EMERALD :

(English) Prohibited Appellation for a malachite.

PSEUDO-JADE :

Prohibited Appellation for minerals resembling jade (mainly used for serpentine) .

PSEUDO-JADEITE :

Prohibited Appellation for a material, a good imitation of jadeite coming from the mines of Tawmaw in Burma and classified among the group of albites.

Density : 2.577

PSEUDO-MALACHITE :

Old Appellation for a Lunnite being a phosphate of copper, having a green colour

Ca₅(PO₄)2( OH)₄H₂0

Hardness : 2.5

Density : 4 to 4.4

System : Monoclinic

PSEUDO-NEPHRITE :

Prohibited Appellation for pagodite .

PSEUDOPHITE :

Serpentine containing aluminium falsely called Jade from Styria ; hydrated silicate of Al and Mg ;

-     - colour : green

-     - Hardness 2.5

-     - Density : 2.6 to 2.85

-     - R.I. 1.576 to 1.579

-     - System : monoclinic

PSEUDOSAPPHIRE :

Prohibited Appellation for la cordierite.

PSEUDOTOPAZE :

Prohibited Appellation for a citrine .

PULLEITE :

Variety of apatite .

PUNAMU :

Maori Name for a nephrite from New Zealand .

PURPURIN :

Very old Name. Glass of a dark red colour, to which was added a metal to make a kind of aventurine glass.

PUSCHKINITE :

Variety of common epidote from the Urals.

PYCNITE :

Variety of yellowish or reddish topaz from Saxony and from Bohemia .

PYRALSPITE :

Name of a group of garnets comprising  pyrope, almandine and  spessartite .

PYRAPHROLITE :

Mixture of feldspath and opal .

PYRALIN :

Variety of celluloid plastic .

PYRALMANDITE :

Contraction of pyrope and almandine (or rhodolite) garnet.

PYRANDINE :

Variety of rhodolite .

PYRENITE :

Variety of melanite garnet from the Pyrenees, France .

Or a variety of grossular garnet of a slightly violet tinted almost black colour.

PYRITE :

Etym. : from the Greek: pyr = fire

FeS₂

Physical and optical properties :

      - Colour : yellow, yellow-grey

-     -Transparency : opaque

-     - Lustre metallic

-     - Hardness : 6 to 6.5

-     - Density : 4.9 to 5.2

-     - System : cubic

The appellation marcassite is often used in the jewellery trade for a pyrite but marcassite is another mineral having the same chemical composition but crystallizing in the ;system, more rare it is more rare and easily deteriorates  (oxidizes very fast in air) excluding its use in jewellery .

PYRITE de FER :

French Synonym for pyrite .

PYRITE MARTIALE :

French Synonym for yellow pyrite or pyrite in general .

PYROGUANITE :

Synonym of apatite .

PYROEMERALD :

Prohibitted Appellation for chlorophane .

PYROIDESINE :

Variety of meteoritic serpentine .

PYROPE :

Etym. : from the Greek : pyropos = eye of fire

alumino-magnesium garnet

Mg₃A1₂ (SiO₄)₃   

Physical and optical properties :

-     - Colour : brown red, red-brown to strong red, carmine

-     -Transparency : transparent

-     - Lustre : vitreous

-     - Hardness : 7 to 7.5

-     - Density : 3.62 to 3.88

-     - R.I. : 1.746 (+0.010 –0.026) (variety non-gemmiferous : 1.705 to 1.770)

-     - System : cubic

PYROPE-ALMANDINE :

See rhodolite .

PYROPHANE :

Synonym of fire opal, equally used for an opal impregnated artificially with wax .

PYROPHYLLITE :

Al₂Si₄O₁₀(OH)₂

Physical and optical properties :

-    - Colour : many colours; mostly greenish , white to yellowish white , grey-white, bluish
-Transparency : transparent to opaque
- Lustre : nacreous
- Hardness : 1 to 2
- Density : 2.6 to 2.9
- R.I. : 1.552 – 1.600
- Birefringence : 0.048
- Biaxial negative
- Cleavage : basal perfect
- System : monoclinic

PYROPHYSALITE :

Variety of topaz .

PYROXENES :

Group of important minerals comprising diopside,  jadeite, chloromelanite, spodumene.

General Formula : X₂Si₂O₆

where X is in general Ca, Mg, Fe, Li, Ti, Al or Na
Common characteristic to all : 2 perfect cleavages of which the intersection is at a right angle (= at 90°)

The pyroxenes are divided into 2 main groups :

-                                  the ortho-pyroxenes : orthorhombic system

                                      contain very little calcium

                                      the more common ones are hypersthene and bronzite .

-                                  the clino-pyroxenes : monoclinic system

                                    contain Ca, Na, Al, Fe³⁺ or Li

                                    comprising : augit, diopside, jadeite, spodumene .