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<br /> redissolution of feldspars or formation of a massive quartz core Foord,E.E.,1986, Crystal chemistry, and origin of color of
<br /> could have occurred.The vein of massive quartz extending out- amazonite, particularly that from the Pikes Peak batholith,
<br /> wards from the roof of the Key-Hole vug most likely represents Colorado, in Modreski, P. J. (ed.), Colorado pegmatites,
<br /> the escape path of the volatiles during venting. Colo. Friends of Mineralogy,Denver,p.77-83.
<br /> The localization of the pegmatite containing the Key-Hole Foord,E.E.and Martin,R.F.,1979,Amazonite from the Pikes
<br /> vug and of the amazonite-bearing pegmatite in the upper pit at Peak batholith:Mineralogical Record,v. 10,p.373-384.
<br /> the Ten Percenter could have been influenced by the presence Glass,J.J.,Rose,H.J.,and Over,Edwin,1958, Notes on the
<br /> of large xenoliths of diorite porphyry and granodiorite in the mineralogy of an yttrium-bearing pegmatite body near Lake
<br /> Pikes Peak magma at the time of pegmatite formation.The sharp George,Park County,Colorado: Amer. Mineralogist,v.43,
<br /> intrusive contacts between the pegmatites and the older p.991-994.
<br /> xenoliths suggest that rising volatiles from which the pegmatites Gross,E.B.and Heinrich,E.W., 1966, Petrology and miner-
<br /> were derived may have been trapped beneath or against these alogy of the Mount Rosa area,El Paso and Teller Counties,
<br /> large irregularly shaped xenoliths, thus arresting the ascent of Colorado. II. Pegmatites: American Mineralogist, v. 51, p.
<br /> the volatiles through the remaining granitic magma long enough 299-323.
<br /> for crystallization to occur.Xenoliths of similar rock have been Hutchinson,R.M., 1986, Granite-tectonics of Pikes Peak
<br /> observed at other pegmatite excavations in the Lake George dis- composite batholith,in Modreski,P.J.(ed.),Colorado peg-
<br /> trict,and the authors hope to be able to document these associa- matites:Colo.Friends of Mineralogy,Denver,p.115-127.
<br /> [ions more fully as a possible guide to further exploration in the Jahns,R.H.and Burnham,C.W., 1969, Experimental studies
<br /> district. of pegmatite genesis: I,A model for the derivation and crys-
<br /> tallization of granitic pegmatites:Econ.Geology,v.(A,p.843-
<br /> 864.
<br /> ACKNOWLEDGEMENTS Odiorne,H.H.,1978,Colorado amazonstone: the treasure of
<br /> Crystal Peak:Denver,Colorado,Forum Publ.Co.,51 p.
<br /> This paper is an outgrowth of a study of the Ten Percenter Simmons, W.B. and Heinrich, E.W., 1980, Rare-earth
<br /> claim for a senior honors thesis at Williams College(Finnemore, pegmatites of the South Platte district, Colorado: Colo.
<br /> 1987); the study was partly supported by a summer research Geological Survey Reserve Series#11,93 p.
<br /> grant from the Bronfman Science Center at Williams during the Smith,D.L.and Rosemeyer,Tom,1986,The Key-Hole vug,Ten
<br /> summer of 1986. The authors particularly wish to thank Dr. Percenter Mine, Teller County, Colorado: Seventh New
<br /> Eugene Foord of the U.S.Geological Survey and John S.White, Mexico Mineral Symposium,Socorro,New Mexico,p.17-20.
<br /> Curator of the Department of Mineral Sciences at the Smith- Tweto,Odgen,1987,Rock units of the Precambrian basement
<br /> sonian Institution,who visited the site shortly after the discovery in Colorado:U.S.Geological Survey Prof.Paper 1321-A,54
<br /> of the Key-Hole vug and who made many helpful observations P.
<br /> about the locality. Wobus,R.A.,1986,The Pikes Peak batholith and associated
<br /> plutons, Colorado, in Modreski P.J. (ed.), Colorado peg-
<br /> matites:Colo.Friends of Mineralogy,Denver,p.70-71.
<br /> REFERENCES Wobus, R.A. and Anderson, R.S., 1978, Petrology of the
<br /> Precambrian intrusive center at Lake George, southern
<br /> Front Range, Colorado: U.S. Geological Survey Journal of
<br /> Barker,F.,Wones,D.R.,Sharp,W.N.,and Desborough,G.A., Research,v.6,no. 1,p.81-94.
<br /> 1975,The Pikes Peak batholith,Colorado Front Range,and
<br /> a model for the origin of the gabbro-syenite-potassic granite
<br /> suite:Precambrian Research,v.2,p.97-160.
<br /> Firmemore,Sara,1987,Pegmatites and host rocks of the Ten
<br /> Percenter mining claim, Teller County, Colorado; unpubl.
<br /> senior thesis,Williams College,74 p.
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