I'KTKOvJKAI'IIY 



1'KTHDl.Kr.M 



Kur purpose* of description rocks may 1* irro]ied 

 in tin- WfM full.)* inn divi-ions: (I.I Igneous 

 Kock*: (II.) Hematite Kocks ; and (III.) Schi- 

 tone Kock. 



I. ly*ni* #orXr(q.v.). Of theae there are two 

 erien (HI rrtistiillme and (b)frntiiiirutnl or '/ 

 Tin- ciystullhie s-rie* include* semi crystalline and 

 vitreous nr glaiwy rock", some of the inure ini- 

 |itant clmractcis of which limy lie noted. The 

 \itnsiiis locks ii-u. illy contain ciystallites and 

 micmlites, and they often -how |x-rlitic and 

 spherulitic structure*. Some varieties an- highly 

 |K.n>u an.l froth like (nee I'lMicKl. Others 

 are more or l s homogeneous, closely compact. 

 and HiniMitli like boMfe-fllM I while \et others 

 are markedly |Miri>hyritic. usually with crystals 

 f saiiidinc ('see l-KUsl'AK). Such vitreous rocks 

 are most usually acidic (i.e. highly siliceous i, 

 hut Iwxic glasses are also known. The semi 

 crystalline nick* are compoMed of crystalline 

 minerals and gla y matter in very variable pro- 

 portion*. The crystalline ingredient* often mow 

 minute inrlii-iiin- of other mineral* (tntlomur)>hx) 

 or of glos.-. \e., which have IM-CII caught up while 

 the crystal wan growing in its molten magma. 

 Krtf|iienlly also the crystals contain minute cavi- 

 ties which "may IK ...... ptj or tilled with -ome liquid 



or Kan. The wholly crystalline locks contain of 

 oonme no glass or non-ditlerentiated matter. It is 

 in tlii- claw of fork*- -many of which are of pin- 

 tonic origin- that liquid cavities arc of most com- 

 mon occurrence in the constituent minerals. In 

 the minerals of -'-mi rn-tallim- and crystalline 

 rocks which have Ix-en erupted at or near the sur- 

 face liquid cavities are less common. In vitreous, 

 emi-crystalline, and crystalline rocks alike the 

 mineral ingredient* art- not seldom dis|ised in 

 linen or bands. Thin in called Jtiij-imi or Jtnultil 

 Hlnicture the ingiedicntM having arrange/! them 

 Helves in this manner while the igneous rock w:is 

 fluid and in motion. Although not unknown in 

 w)ine h.il.HTxstiilline rocks, it is a structure which 

 i- more clianu-terixfic of the vitreous and semi 

 crystalline ntckx which have Ix-cn |>oured out at 

 the earth's surface as lavas. The appearance of 

 the oiiginal mineral con-mnent- of many igneous 

 rocks shows that their crystallisation cannot have 

 taken place coiitciniKiraneously, In most cu-es it 

 can ! shown that tliey helong to two sta^e- in the 

 i .in-oli. liilicill of the riM'k of which they form a p;nl. 

 Thiix. in many crystalline and emi ci \stallinc nx'ks 

 we reailily ifistingui-li a crystalline <n semi.iv- 

 talline ground nnt-s. scattered through which occur 

 larger ciystiil-. many of which may In- hroki'ii ami 

 i-..n.|.-d Tlii-M* latter are l>cllc\i>d to havi- ci \ - 

 t.ilh-e.| while t lie molten rock :- -till at a eon 

 niderahlc depth U-low the siufacc. Afteiwaids, 

 when the fluid mas- was poured out at or near the 

 urfiw-e. and cooled rapidly, the smaller minerals 

 and glossy matter of the ground-mass were funned. 

 Although llne two clasHex of minerals can In 1 seen 

 mo-t '-learly in rocks of a tracliv toid and por]ihv- 

 ritic aojioct, yet even in granitoid rocks evidence of 

 two tagi-o or periods of consolidation can often ! 

 detis-||. The general chariwter of fnigluental 

 ivniHMt. ro-k i di-.-iis-ed under A'.i.l.uMKKATK, 

 K. ami II.VKOI s KIH-KS. Mo-t of the rock* 

 mentioned in the following tallies have separate 

 articled aiwigned to them. 



I'll Vttrtwi and fry/ill/' 

 I < linn., i .p If,. K. : ,,!>!. |U>M. |,n, l,-i.,n. i .irnrturml virir- 



Ufi -i< <nr~MM r-k. u i-rlit-. |Ji--riiht nn-k. |n ..... !!. 

 yt*. l'|ni*. nrtliiM-Uv-iii^iiliyry, qturl-z* 

 e. (null". 



1 PiuriTnii> 

 4. "i IT mil 



a: Bfpbvliftt-baflalt, 



or llaiDonrn : JrfcrlU, Unoltto, 



tanoOT Bocu : nriou MrpcnUnr rocka. 



(i) Fragmental or C/,i<,-ti'i- 

 Vulcanic sntlimirrmtr. vi.lrnir Im-rcu, tulT; vulranle Mini, 

 uhM, diut, bl<>cki>. Upilli. IH) bointw. 



II. Derivative Hoi-/.". .\- water has iilaye*! a 

 verv prominent part in the formation of tliis great 

 division of riM-ks, the-eare frequently termed aqueou* 

 or netlintrnliiri/. Such lH-ing the origin of by far 

 the greater number, we tind that they generally 

 occur in layers or lulls, hence the name hy which 

 they are also widely known strntijittl rocks. 

 Some of the memliers of thi- division. lmwe\er, are 

 not of ai|iieous origin, while others do not occur in 

 U'iU. Hut they are all alike in so far as the 

 materials of which they consist have been derived 

 by epicene agents from the degradation of pie 

 existing rocks, minerals, and organic liodies. 



1. GBAVKL AND SAND RIK-KS : n'k-debri and bncia ; i!n- 

 waah and brick-tarth ; iil and -.iil.Mul : -lun^lf mid uravd, 

 conglomerate ; md, nandntom, and ^ to. 



2. CLAY ROCKS: kanlin, iiijarlay. iim-hiy. lirirk-clay, fullcr'a 

 earth, bouldw-clay or till, Imim, iiiiiilsiiini>, ri;ill;ii 

 shale. 



3. CAUCAREOCS RCH-KR : ihnrstinir inl IU many vai 

 (uch an calc-intr, clialk, in.lite, marl, coral-rock, 



Inloiinl.- or iiiiiLMH-sinn limestone. 



4. IBUMHTONK Roicxa : liinuuitr. hirniatitc, ipatliic iron ore 

 t -ili i !> *i-l i iir, lilackband ironstone), magnetic iron ore. 



6. SILICKOI s HtN-Ka : ailiceouH sinl,-i. Hint ' 

 lydian IIIP, jaaprr, Ac.), trlpoli and radiolarian 



A. PHOSPUATIC KIM KS : bone-bnoelM, guano, ooprolftaa 



7. CAI; K.IIKS: iKut, lignite, <MI and il van. 

 Hiiihnii-ilc. nil-shale, |-tr..]. um. asplialt. 



8. OVPSUJI AND HAI.ITK GKOIII-: anhydrite, gypninn, and rock- 

 tt. 



III. S<-liixtnsr /,'(/. .v. The more representative 

 rocks of this division are more or less crystalline 

 and schistose or foliated (see FOLIA i ION ). Some. 

 however, show faint traces either of crystalline, or 

 foliated structure : w liile others, although distinctly 

 crystalline, are not schistose. Again, some of the 

 rocks are fragmental. with more or less of super 

 induced crystalline stnicture. Many schisto-e 

 rocks are clearly of metamorphic origin. They an- 

 al tered igneous and derivative nn-ks. The origin 

 of others is still oWnre. See ARCHAEAN SVSTK.M. 

 GEOLOGY. 



Quartz-rock, quartz-M-lii*t luiHefllnta, schitoe ciint-loni' i 

 at--, i-lay-late ami its \:m,-t-. pliyllili-, ini.-Ji .-1iit. talc- 

 -chist, obtoritc-achiat, amphibole-MhUt (actinolltB-aeblat, 

 hiirnlili-iiili- s-lut V Kiii-ii.-., Kninulit*, eel". i.-k, 



marble. 



See Rutley, The Ntudy of Rodu (ls7'.'i; Match, 

 Prlrotixiy (18!ll); Cole, Aidl in /V.i.o. .. 

 (ll| )'; Ijuwulx, Kin fiiltriiiKi in 'lit OoMluUkn I Ixso,: 

 Kalkowsky, fV, ,n, ,,i, ..',/ l.,thnl,nr (Issii); .iKimcttaz, 

 La Rochet (1KK4). Morv advanced works are Teall, 

 Hrilith 1'ttr-tint/thy (lt8); Kimqiie and Levj-, M, 

 (iloiiie lUicrotiraphinve (1879); Bownbueb, M 

 tl,i>liifeht I'hviitMjmpnit d. Afineralii" < '""S); 



Xirki-1, .Vik'rofkiijjucke Barhafenheit d. Mineralitn u. 

 (/<nn<(1873). 



IV 1 1* I) It'll III (trm 1 1 I. at. fa Ini, a lock, and ulrinii, 



oil), i (M-k -oil, an inflammable, dark lii|iii<l.c--entially 

 compii-ed of cailimi and hydro 

 gen, which exudes from I In- 'earth 

 in various parts of the world. 



(1) lifiierttl History. It is [rapoeelble to state 

 when petroleum wan first discou-rcd. In some 

 form it si-ems to have !>een applied t<v the use- of 

 mankind in the earliest periodl known to historv. 

 The ruins of Nineveh and Itabylon indicate that 

 the asphaltic mortar used for their walls and 

 buildings was made from a |iartially evaporated 

 |ietrolcmii, obtained, doubt le , from the springs 

 of Is, on the Euphrates. This is probably the 

 'slime' of the Old Testament Scriptures (Gen. 

 xi. 3). Herodotus (i. 110: iv. l!lf.]. "lOO B.&. 

 writes of the spiings in the i-land of /ante. 'I 

 have myself seen pitch ilrawn out of a lake 

 and from water in /acynthus,' &c. Stralsi ( xvi. 2) 

 refers to the bitumen found in the valley of 

 Judea, and sold to the Egyptians for embalming. 



OopTrlcbl imi. 1HT. .n.l 

 l0(i In Ihr f. S. br J. H. 



Llppln.-..' 



