P Y E 



[375 ] 



P Y B 



yellow, and sometimes to brown. 

 It possesses the hardness of quartz, 

 striking fire with steel, and emitting 

 an odour of sulphur. Specific 

 gravity from 4*10 to 4'80. Before 

 the blow-pipe it exhales a strong 

 odour of sulphur, and yields a 

 brownish. globule. It is composed 

 of sulphur and iron; iron 47-85, 

 sulphur 52 '15. It occurs in almost 

 every rock, stratified or unstratified. 

 The shining yellow streaks so com- 

 mon in our coals afford familiar 

 examples of pyrites. 



PYRI'TIFEROTJS. Yielding or contain- 

 ing pyrites (sulphuret of iron). 

 "These beds are underlaid by 

 sandy pyritiferous shale." Murchi- 

 son. 



PY'ROCHLORE. The pyrochlor of Wer- 

 ner. Octahedral titanium ore. 



PYRO'GENOTJS. (from Trvp, fire, and 

 ryej/i/aw, to produce, Gr.) Pro- 

 duced by fire, as rocks of igneous 

 origin. 



PYROLU'SITE. Another name for the 

 common ore of manganese, as pris- 

 matic manganese ore. 



PYRO'METER. (from irvp t fire, and 

 /merpov, measure, Gr.) An instru- 

 ment for measuring intense degrees 

 of heat. The most celebrated 

 pyrometer is that invented by Mr. 

 Wedgewood, the extremity of his 

 scale reaching to 240 Wedgewood, 

 or 32277 Fahrenheit. 



PYRO'PE. (from TrvpwTros, Gr. pyropas, 

 Lat.) The Pyrop of Werner; 

 Grenat, rouge de feu, granuliforme, 

 of Haiiy ; Grenat pyrope of Brong- 

 niart ; Bohemian garnet of some 

 authors. A deep blood-red variety 

 of dodecahedral garnet. It consists 

 of silica 40-0, alumina 27'6, oxide 

 of iron 16'0, magnesia lO'O, lime 

 3-5, chromic acid 2-6, oxide of 

 manganese 0*3. It occurs in small 

 masses or grains. It is generally 

 transparent, with a splendent, vi- 

 treous, conchoidal fracture. Specific 

 gravity from 3-7 to 3 9. It refracts 

 double, and is sufficiently hard to 



scratch glass. Its fine blood- red 

 colour is supposed to be owing to 

 the presence of chromic acid. It 

 is found imbedded in serpentine, 

 wacke, and trap-tuff in Ceylon, 

 and different parts of Germany. It 

 is also found in some alluvial soils, 

 accompanied by sapphires and 

 hyacinths. As a gem it is highly 

 prized. 



PYRO'PHORTJS. (from 7rvp, fire, and 

 and 0o/)09, bearing, Gr. pyrophore, 

 Fr.) A substance which has the 

 property of igniting merely on ex- 

 posure to the air. It is an artificial 

 production, and may be variously 

 prepared. M. Gay Lussac formed 

 a pyrophorus of one part of lamp- 

 black and two parts of sulphate of 

 potash. 



PYROPHY'LLITE. An earthy mineral, 

 described by Hermann of Moscow, 

 occurring in the Ural mountains. 

 It is of a light green colour, has a 

 pearly lustre, and may be divided 

 into thin and transparent laminae. 

 It is found in fibrous radiating 

 masses, and small elongated prisms, 

 sometimes with terminations, whose 

 form is not however ascertained. 



PYROPHY'SALITE. A variety of topaz. 

 The Pyrophysalith of Hisenger. 

 This mineral which some authors 

 consider to be intermediate between 

 topaz and schorlite occurs princi- 

 pally at Finbo, near Fahlun, in 

 Sweden. It is of a greenish- white 

 and mountain green colour, trans- 

 lucid or opaque, and sometimes 

 prismatic. On burning coals it 

 phosphoresces, in consequence of 

 the fluate of lime with which it is 

 mixed ; from this property it has 

 obtained its name, which is derived 

 from the Greek. It occurs massive 

 and crystallised, and may be regarded 

 as a coarse opaque variety of topaz. 

 Specific gravity 3-451. It scratches 

 glass, but is itself scratched by 

 quartz. It contains alumina, 

 silica, fluoric acid, and a trace of 

 lime and iron. 



