422 



MINERALOGY. 



Geognosy. These are, 1. Small beds of mica-slate that alternate 

 "*" "Y"'' with small granular sienite. 2. Beds of quartz. S.Beds 

 of compact limestone impregnated with steatite, and in- 

 termixed with serpentine. 



5. Metalliferous minerals. It contains many metal- 

 liferous minerals. They occur more frequently in veins 

 than in beds ; but as the porphyry is seldom stratified, 



Metallife- 

 rous mine- 

 rals. 



Forma- 

 tions. 



Form of 

 mountains. 



Geographi- 

 cal distri- 

 bution. 



is difficult to determine to which of the two kinds of re- 

 positories they belong. The richest mines at present 

 known, those of Mexico, are situated in enormous veins 

 that traverse sienitic porphyry. The mines of Hungary, 

 the most considerable on the continent of Europe, are 

 situated in the same kind of porphyry ; and it would 

 appear that the famous mines of Cyprus, so much ex- 

 tolled by the ancients, were also in porphyry. The 

 numerous veins of lead, copper, and silver, worked at 

 Giromagny, in the Vosges, are in a porphyry tract. 

 6. Formations. Porphyry occurs in imbedded masses. 



3. Form of Mountains. Mountains of quartz-r 



are often conical, sometimes even peaked, or they are F """~ y 'T"' 

 crenated. . m out ain 8 , 



4. Geognostic Situation. It occurs in beds and moun- Geognostic 

 tain masses, in granite, gneiss, mica slate, and clay situation, 

 slate, and indeed in a certain degree associated with 



most of the rocks of the primitive series. 



Geographical Distribution. It abounds in many dis- Geographi- 



and as the surface of superposition, is not often seen, it Geographical Distribution. It abounds in many dis- ^ 

 s difficult to determine to which of the two kinds of re- tricts in Scotland, as in the islands of Jura and Isla, the 



Shetland Islands ; on the mainland, in Sutherland, 

 Caithness, Inverness-shire, Argyleshire, &c. 



CLASS II. TRANSITION ROCKS. 



Ubergansgebirge. Werner. 

 Transition Rocks. Jameson. 

 Terrains Intermediates Daubuisson. 



The rocks of the primitive class, as already remark- 

 ed, are distinguished in a general view by their highly 



tion. 



----- *.* J 1 Cvij <*1 1 uio kiu i^ LI iou^.v.1 * ** ti-"^-*. * " "j * & J 



beds, and veins in granite, gneiss, mica-slate, and clay- crystalline structure, and want of petrifactions, or fos- 



slate. sil organic remains. In some countries we observe 



7. Form of mountains. They are often conical, some- rest ; ng upon t h ern , and even alternating with them, a 

 - -shaed. 



times like truncated-cones, or appear dome-shaped. 



8. Gcograpluc distribution. It occurs in the Shetland 

 islands, in several of the Hebrides, and on the mam- 

 land of Scotland, in Sutherland, Ross-shire, Inverness- 

 shire, Perthshire, &c. In England it is met with 111 

 Cornwall, and in other districts. On the continent oi 

 Europe, it occurs in Sweden ; it forms a part of the 



series of roc k S) o f wn ich clay slate is a predominating 

 mem b er , having less of the crystalline aspect, and 

 w jjich contains fossil organic remains. Werner consi- 

 ders th j g et of rocks as i nterpose d between the grand 

 geries of pr i m i t ive and secondary rocks; and that, al- 

 ^^h ; t occasionally alternates, on the one hand, with 

 the pr j m j t i v e, an d on tne other with some members of 



Utei. 



, , 



Vosges, and rises in mountains in the granite district of the secon d ary c i asS) st ill its characters are so well mark- 



Forez, also in France. It has not been met with in the e ^ that ne views it as a distinct class, to which he 



Pyrennees, nor is it mentioned as occurring in the Alps the name Transition, from its forming, as it 



of Switzerland, nor in the northern side of the grand wer ^ the trans ; t j on or pass age from the primitive to 



chain of the Alps, but it occupies a considerable tract the seconc ] ary roc ks. Although some mineralogists have 



on the southern side, from the lake of Como to Carin- a k an doned this view, and now arrange the transition 



thia and Carniola. It appears, although not very abun- roc j js a i orl g w ith those of the primitive or secondary 



dantly, in Silesia, Saxony, and Thuringia, and forma c j asseSj we are st iu inclined to consider them as de- 



extensive tracts in Hungary. It abounds in some dis- gerv j ng a separate place in the geognostic system. It 



tricts in Upper Egypt, Siberia, and in North and South. Js true ^ that the transition rocks are but a continuation 



where there are considerable quarries of porphyry. 

 X. Quartz RecL 



America. o f t ne primitive, and, on a general view, might with 



Uses It was formerly used extensively in ornamen- propr j ety be considered as a portion of that series ; but 

 tal architecture, and is still worked in considerable their Bedded fossil organic remains, less crystalline 

 quantity as an ornamental stone, in Elfdal ir^ Sweden, aspectj an j p ar ticular rocks, such as greywacke, appear 



to characterise them, if not as a distinct class, yet as a 

 separate group in the grand series of rock formations. 

 The following are the rocks of this class : 



Characters. 



Structure. 



Metallife- 

 rous mine< 

 ral. 



Quartz fels. Werner. 



uartz Rock. Jameson. 

 uartz en Roche. Daubuisson. 

 Quartzite. Brongniart and Bonnard. 



1. Characters. Quartz occurs not only as an essen- 

 tial constituent part of granite, gneiss, and mica slate, 

 and disseminated in beds and veins in these rocks, but 

 also in mountain masses and mountains.^ Quartz-rock, 

 properly so called, is generally of a white colour, and 

 sometimes reddish or bluish. It has a granular struc- 

 ture ; the concretions vary from the smallest size visi- 

 ble to the naked eye, to that of an egg, or even larger ; 

 or it is compact. It. frequently contains grains of fel- 

 spar, and also scales of mica. When the felspar and 

 mica increase in quantity, it passes into granite, or into 

 gneiss, when only the mica into mica slate. 



Structure. It occurs either distinctly stratified, or 

 massive, and without the stratified structure. 



2. Metalliferous Minerals. It often contains dissemi- 



" . i * 11 i i i 



1. Grey-wacke. 



2. Transition limestone. 



3. Granite and porphyry. 



4. Gneiss, mica-slate, &c. 



5. Serpentine. 



6. Quartz-rock. 



7. 'Red sandstone. 



8. Transition-trap. 



9. Gypsum. 



I. Grey-tvaoke. 



Grauwacke. Werner. 

 Greywacke. Jameson. 

 Traumate. Daubuisson. 

 Psamite. Brongniart. 



Breche, Poudingue, and Gres, of tome French 

 geologists. 



Composition. It is composed of angular or other Composl- 



* ft i _ T 1' _1_A. 1 _1 . ..!..*,, tinn. 



Gry- 



wucke. 



pyrites, and blende. 



ance copper- portions of quartz, felspar, Lydian- slate, and clay-slate, ^on- 

 connected together by means of a basis or ground of 



