MINERALOGY. 



Origin of Coal. Two opinions are entertained in 

 regard to the origin and formation of coal. According 



427 



Geognosy. 



Xe red or 



arirgated 

 aodstone. 



Characters. 



to the one it is of vegetable origin ; and according to 

 the other, it is an original chemical formation. Its 

 chemical properties, and numerous accompanying ve- 

 getable remains, which are sometimes changed into coal, 

 are the principal facts adduced in favour of its vegeta- 

 ble origin ; while its distribution in regular conforma- 

 ble beds, its occurrence in veins, and embedded masses, 

 its manifold alternations and connections with different 

 strata, some of which never contain vegetable remains, 

 its rhomboidal structure, external characters, its con- 

 nection with glance coal, on the one hand, anil with 

 bituminous shale and sandstone on the other, are the 

 appearances which are considered as illustrating its for- 

 mation as an original deposit, from a state of chemical 

 solution. 



1 1. \ev lied or Variegated Sandstone. 

 Banter Sandstein. Werner. 

 Red Gron lish Geologists. 



New Red. Auckland. 



New Red or Variegated Sandstone. fameto*. 

 Second formation de Ores, t Gret avec argile. 



Daubuuton, 

 Gres Bigarre_ French Geologists. 



Characters. It is small granular, with an argilla- 

 ceous, or marly bns. Its colour varies extremely, be- 

 ing frequently disposed in bands or zones, of red, 

 grey, green, yellow, and brown, hence the name varie- 

 gated, given to it by Werner. These different colours 

 are owing to the different states of oxidation of the iron 

 in the basis or cement, but it may be remarked, that 

 these deep colours are often very superficial, the interior 

 of the rock being of a grey or white colour, while the 

 fxterior, by exposure, becomes brown or red. 



ThU sandstone frequently contains masses of various, 

 ly. coloured clay or marl, with are often lenticular, and 

 vary very much in size, and contribute very much to 

 increase its liability to decomposition. The clay if 

 sometimes greasy to the feel, and forms a kind of ful- 

 ler's earth. Although the mo<t common cement or ba- 

 sis of this sandstone is clay, yet some beds have marly, 

 and others a quartzy basis. 



It sometimes contains mica, and sometimes in such 

 quantity that sandstone passes into sandstone slate. 



It alternates with beds of a red-coloured clay, or 

 marl, which is often slaty, and generally intermixed 

 with sand and mica, and sometimes passes into sand- 

 stone slate. These beds are sometimes of great thick- 

 ness, and from their being frequently short, and very 

 thick, appear like great imbedded masses. Some- 

 times the marly or calcareous basis increases so much, 

 that the sandstone passes into lime-tone. The colour- 

 ing principle in the clay is occasionally no abundant in 

 some parts of the beds, that a red crayon is formed. 

 The thick beds of clay occur principally towards the 

 upper part of the formation, which indeed is principal- 

 ly red clay. Sometimes beds of conglomerate occur as- 

 sociated with the sandstone, marl, and day. 



Ordinate lifds \, Limestone Beds of limestone 

 ate beds. are . met with in this formation ; but, in general, the 

 limestone is very impure, being mixed with clay and 

 sand ; and thus forms a more or less arenaceous marl. 

 Oolite or '-' Oo/i/ or Roe-itonr. This curious kind of lime- 

 ror-stooe. stone occurs but in small quantity, and generally in beds 

 varying from a few inches to two or three feet hi thick- 



ITM ore. 3. /ro* Or*. It sometimes occurs in considerable 



Heavy 



spar, sul- 

 phate of 

 tfflrytrs. 

 Celestine 

 or sulphate 

 of stron- 

 tites. 

 Gypsum. 



Rock rait. 



Copper, 

 ore. 



Coal. 



Petrifac- 

 tions. 



Geognostic 

 situation. 



Geographi- 

 cal distri- 

 bution. 



Third 



sandstone 



formation. 



quantity, and is generally the red ore. It is either in 

 imbedded portions, disseminated, or so minutely dif- 

 fused, as to colour some of the sandstones of a deep 

 red colour. 



4. Heavy Spar, Sulphate of Barytet This mineral 

 occurs in veins in the sandstone. 



5. Celestine or Sulphate of Strontitet. This mineral 

 occurs in the clay and sandstone, in the form of veins 

 and beds, near Bristol. 



6. Gypsum It occurs in imbedded masses, and beds 



and veins, in the marl or sandstone of this formation. 



7. Rock So/f The salt of the principal salt mines 



in Europe is arranged in beds, and imbedded in this 

 formation. 



8. Copper Ore Traces of copper ore are rarely met 

 with in this formation. 



9. Coal ThU mineral occurs very rarely, and usual- 

 ly in inconsiderable beds. 



10. Pet rij act font. The most frequent petrifactions 

 are pectinites, pinnites, pholades, turbinites, and large 

 ostracites ; and sometimes petrified wood, and impres- 

 sions of leaves. 



Geognoflic SUualion.}t rest* upon the magnesian 

 or second limestone, and sometimes even alternates 

 with it, and is immediately covered with the oolite for- 

 mation. 



Geographical DitiributioH^lt is very widely dis- 

 tributed formation in England, extending, with little 

 interruption, from the northern bank of the Tees in 

 Durham, to the northern coast of Devonshire : Also oc- 

 curs in Scotland, particularly in the southern division. 



III. Third Sandilone Formal ion. 

 Green Sand of English Geologittt. 

 Third Sandstone Formation. Jameson. 

 Troisieme Formation de Gres. DaubuitsoH. 

 Quader- Sandstein Werner. 

 Gres presque entierement quartzeux. 



This formation, the characters of which are still but 

 imperfectly known, is described by English geologists, 

 under the* name Green-sand, and according to Mr. 

 Buckland, is associated with various strata. 



Character*. The sandstone is composed of particles Characters, 

 of white quartz, which are either cemented by a calca- 

 reous bmsis, or are united without any cement, and fre- 

 quently contain scales of mica, and embedded grains, 

 and portions of a green substance, of the nature of chlo- 

 rite or augitc. 



The quartzy particles are sometimes to arranged and 

 connected, that the Kandttone is as massive and compact 

 a* quartz, while, in other instances, it occurs in the 

 state of loose grains or sand. 



It frequently contains imbedded cotemporaneous 

 masses of chert, and the same mineral occurs also in 

 beds ; and sometimes both the green-sand and chert are 

 traversed by veins of calcedony. 



Subordinate Betlt. Limestone of a blue and reddish Subordi- 

 colour in the form of beds, if occasionally met with, and n * le bedt - 

 sometimes the limestone is also distributed through the 

 sandstone in masses of varying magnitude. Mr. Buck- 

 land enumerates the following beds as occurring in this 

 formation : 1. Lead-coloured clay ; 2. Micaceous and 

 sandy blackish clay, with disseminated green earth , 

 3. Iron-sand, usually red and yellow, and containing 

 subordinate beds of clay, ochre, and fuller's^earth, ei- 

 ther pure, or inclosing nodules of heavy spar. 



Petrifaction* It contains musculitex, mytillites, and Petrifae- 

 tellinites, and sometimes impressions of leaves and stems tions. 

 resembling those of the palm tree and the pine. 



