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T}iE QL-ARRIES OF THE CASTLE ROCli AREA 115 >tfa. ~~n B1as. Jevls Rose Heacl:c To either side of the highway between Sedalia and Palmer Lake stand a number of isolated hills and small mesas, wearing pr~minect rock cap. The geologleal structure of this stone c•apFing gate rise to the quarry industry in Douglas County and has p:oced a unique end valuable source of revenue. Ceologuts tell as that originally the whole floor of the Galley -;!•:~ r:l Palmer Lake nud Sedalia was encored by a lace flow from some t'olranic fisure. the ease; location of which is unknown.' In time most of this Volcanic covering lass removed by erosion, so that pots r,tit- the remuents remain trhic?: cap suci; promontories as Rasp;:er: 73utte, Larkspur Bu!t.~. and DRtt';nu Butte.' The largest outc•rcppiug is five to se'~eu n:i':e3. >,o.aheest of the toml et Castle R.eck, tear the Castle Iin.;~L- $e rt-:rr. Yllc "Casrl.• Hoek" whie6 tol:crs over the totrn of that caalq s3c•rds the motorist an esee;lc:a vu•~ cf this lava cap an c. rilastraL^- haw, as the sur- rot;r~iinc Fart t~~c wor:: aw3t•. talc hard covcriug pcotecb:ri and i!C;o c, : +Lc- srth beneath it urlii in *in,e R till] was Icrnlec rising ever Si~Ler rls tl•e calla}' Snor ~-^r: erode;i shat-. The rh}'elite or !acs it, the fiutc is a 5ne greiacd, li~•ht eoiorerl fain}' hard, rather porous rock :cith a eomyosition Rpprosi- matel}' the slime as granite. The rhyolitc howet•er is much fixer grained then granite because it poured :cr~3 s volcano as a molten lel'x and spread over the surrounding ground surface in a thin sheet. The rock is light colot'ed, due to the fact that it is made up chiefly of quartz. orthoclase feldspar, and plagioclase feldspar.° For use as a building stone the rocs: has a pleasing gray to pink color, is readil;- worked, stands tceather Real and is escep- • tionall}• strong for its a-eigbt. \\'hen crusLtd it makes excellent material for road r.r runway base courses and for concl•ete aggre- gate.' The first person to recognize the nature of this rock capping was Silas \C. ;badge; on his ranch two miles south of Castle Rock stood one of these peculiar isolated buttes. One day, armed with pick end shove], he climbed to the top of his stony mesa and sank e number of prospect holes through the layer of loose dirt and fine ~ rock lchich covered the hill. Everywhere, he struck a pinkish gray, hard rock, through which be could not penetrate. Curious as to the nature of this porous stone he pried loose a number of pieces end shipped them into Denver to be assaced. The returned report slated that. although the rocL- specimens contained no precious metal, stiL', due to its structure it would make an exce]- lent building stone and, if readil}• accessib]e, might be quarried with profit and shipped into Denser, as that sit}•, now rapid]y growing. was demanding more and more building material. As earl}' as loi2 Silas _lfadge started taking out rock from his quarry. It lt'65 fl 610K process. Before any rock cou]d be cut or moved the to}t of the butte must be cleared of dirt elld loose rock; this work in quarry terminology is called stripping. ~+ road must be +li. S. Geologln.l Surve3', Cattle Rock Follo i\o. 19t. V6id., Ceolog7cal >.r. p. Mrs. Ethel F. LtcCarN)'. Cftlef Clerk. State Bureau or lflnee. Dent'er. 'COIO:aOo State School or Mlnra, PuitdinD Sfmiu o) Colorado, li.