MINERALOGY. 



dty. met wkh ; viz. madreporites, ammonites, tellenites, and 

 -, ' branches and trunks of trees variously bituminised. 

 GeognoMic Geognottic Situation. It is contained in, or rests upon 

 tituation. the new red or variegated sandstone. 

 Geographic Geographic Situation. It occurs but in small quan- 

 itu*tion. tities in Scotland, whereas in England it is abundant 

 in some districts, as in Cheshire, Worcestershire, &c. 



431 



trip. 



Gieenr. 'i.e. 



2. Second Secondary Gypsum. 



Secood as- This formation occurs along with the rocks of the 

 rondjry pris formation, and will be described under that head. 



IV. Secondary or Flcetz Trap-Rocks. 



I ruler tl\i- division we include, as a matter of con- 

 venience, the secondary trap sand porphyries. \Ve shall 

 first describe the traps, and next the porphyries. 



FloeU Trap. Werner. 



The rocks of this series are compounds of augite and 

 or aViti felspar, with occasional intermixtures of hornblende. 

 The following are the different kinds of these rocks, 

 viz. 1. Greenstone ; 2. Amygdaloid; 3. Wacke; 4. Ba- 

 salt ; and 5. Trap tuff*. 



1. Greenstone. Jameson. 

 Griinstein Werner. 



Compai- Composition. Is a granular aggregate rock of augite 

 and felspar. The felspar is sometimes red, but more 

 frequently of grey colour, and the augite is almost al- 

 ways blackish- green. It varies from rather coarse gra- 

 nular to the compact, when the concretions are only 

 discernible by means of their glimmering, and then 

 the mass has much of the basaltic character. 



Imbedded Minerals. These are augite, basaltic horn- 



crala. blende, felspar, calcareous spar, diallage, and iron py- 

 rites. In the true porphyntic greenstone, as that of 

 Arthur Seat, the imbedded crystals are of felspar. 



Structure. Structure. It is sometimes amygdaloidal, and the 

 amygdaloidal portions are of zeolite, calcareous spur, or 

 quartz. Frequently it is disposed in columns or pil- 

 lars, and these are again composed of globular and con- 

 centric lamellar concretions. Sometimes the whole 

 mass of the bed is arranged into balls or globular con- 

 cretions, or is disposed in tabular concretions. The 

 beds vary in thickness from a few inches to m.iny fa- 

 thoms, and in the thicker beds stratification is discern- 

 ible. 



Csttsnpa- Cotemporaneoui feint. Very often beds of second- 

 **" ary greenstone include veins of various descriptions 

 that appear to be of cotemporaneous formation with 

 the rock. The following enumeration contains a few 

 of the veins met with in the secondary greenstones of 

 Scotland : 



1 . Calcareous spar. 2. Calcareous spar and quartz ; 

 the quartz sometimes in the form of amethyst or rock- 

 crystal, but more frequently as common quartz. 3. 

 Calcareous spar, common quartz, and calcedony. 4. 

 Calcareous spar, heavy spar, and quartz. 5. Calcareous 

 spar, and heavy spar, with glance coal. fi. Calcareous 

 spar, heavy spar, and brown hematite. 7. Quartz, with 

 red hematite and iron glance. 8. Calcareous spar, brown 

 spar, and sparry iron. .0. Calcareous spar, heavy spar, 

 prehnite, and zeolite. 10. Felspar, either grey or red. 

 11. Iron pyrites. 12. Red cobalt. 13. Yellow copper 

 pyrites. 



fetnfac- Petrifactions. FOMI! organic remains are of rare oc- 



** currence in trap rocks. Petrified shells have been 

 found in greenstone, and also in that slaty rock (slaty 

 ". felspar) frequently associated with it. 



Geognottic Situation, Occurs in beds, imbedded Geognosy. 

 masses, and veins in the old red sandstone, coal forma- ^ < 



tion, variegated sandstone, and in various secondary ^" 



. . . . . ..* situation. 



limestones. \ ems occur in primitive and transition dis- 

 tricts. It is occasionally associated with a secondary 

 syenite. 



Geographic Situation. It is a very abundant rock in Geograph 

 the sandstone and coal districts of Scotland, and is not situation. 

 unfrequent in many primitive and transition tracts alt-o 

 in this country. Vein-* of it traverse the coal forma- 

 tion in the north of England, and although met with 

 in other part.-, of England is by no means so abundant 

 there as in Scotland, 



2. Amygdaloid. Jameson. 

 Mamie la tein. Werner. 



Amygda- 

 loid. 



Characters. This rock has a basis or ground inclu- Characters, 

 ding amygdaloidal portions of various minerals. The 

 basis or ground is generally an intimate combination 

 of augite and felspar in a very imperfectly i r\ -ullized 

 state. Its colour is frequently green ; sometimes red- 

 dish when much iron-shot ; or nearly black when the 

 predominating material is augite. The amygdaloidal 

 masses vary in their nature ; some are calcareous spar, 

 or brown spar, or heavy spar, while others are green 

 earth, quarts, steatite, or lithomarge. 



Imbedded Minerals. Besides amygdaloidal masses, imbedded 

 the rock sometimes contains crystals of felspar, augiie, mineral*. 

 or hornblende, thus affording examples of the union of 

 the amygdaloidal and porphyritic structures. 



i . urr. It occurs in columnar, globular, and also Structure, 

 in tabular distinct concretions; and occasionally it i 

 imperfectly stratified. 



Geognoslic Situation. It generally occurs in mouit- <.;<. ir 

 tain mssses or beds, and sometimes in veins, and prin- situation, 

 cipally associated with rocks of the sandstone and lime- 

 stone series. 



Geographic Situation. It is an abundant rock in the Geogra- 

 touth ami middle divisions of Scotland, both mi the phic titua- 

 mainland and among the islands, as in Arran, Mull, lion. 

 Rum, Eigg, C'anna, and Skye. 



S. Wacke. Jameson. 

 Wacke. Werner. 



Wacke. 



Characters.- Thin rock has generally a greenish-grey characters 

 colour ; less frequently it is reddish, or of a brown ur 

 blackish cast. The fracture surface is dull, or only 

 faintly glimmering, and the fracture is even, or flat 

 conchuidal. It is opaque, and more or less shining in 

 the streak ; soft ; sectile ; easily frangible ; and speci- 

 fic gravity about 2.8. 



CoMSMMsVioN. It appears to be a very intimate com- Compod. 

 bination of earthy augite and earthy felspar. tion. 



Structure. Sometimes occurs in globular and imper- Structure 

 feet columnar concretions, and occasionally it has the 

 amygdaloidal structure. 



Geognottic Situation. It occurs in bed*, imbedded Geognootic 

 maws**, and in veins in sandstone and limestone. situation. 



lyra/thic Situation It occurs along with amygdav- Oeogra- 

 loid and greenstone in our coal-fields in different parts phic itu. 

 of Scotland, and also in the new red sandstone and some Hon. 

 other secondary formations. 



'isalt, Jameton. 

 Basalt, Werner. 



Hsu . 



Character*. Its colours are generally greyish, or Charact< r- 

 greenish-black, and rarely inclines to grey. Internally 

 it is dull or feebly glimmering. The fracture in thv 



