676 REPORT OF NATIONAL MUSEUM, 1897. 



original substance has been changed to a new compound, or has disap- 

 peared and been rephiced by another to which the habit of crystalliza- 

 tion or structure jiresented does not belong. Pseudouiorplis are of 

 three kinds: Substitution, deposition, and alteration. 



Pscudoniorphs by substitution coni})rise those cases in which there 

 has been a more or less gradual replacement of the original nuxterial 

 by another without chemical action taking place, and the form and 

 structure of the original substance is preserved. 



J'Jxiniiplin. 



Quartz, SiO,., after linorite, CaFi, Cornwall, England (Cat. No. 82106, U.S.N.M.); 

 cassiterite, SnO.., after orthoclase, KAlSi:(0«, Cornwall, England (Cat. No. 13431, 

 U.S.N.M.); Copper, Cu, after aragouite, CaCOs, Corocoro, Bolivia (Cat. No. 10579, 



U.S.N.M.). 



Pseudomorphs by deposition fall under two heads: Incrustation, in 

 which a layer or crust of a mineral deposited upon the surface of another 

 substance assumes the form of that substance in a more or less perfect 

 manner; infiltration, in which case a cavity or mold made by the 

 removal of a substance has been filled by the dei)Osition of a mineral. 



Examjilcs. 



By incrustation: Qnartz, SiOj, a^ter calcite, CaCO, Schneeberg, Saxony (Cat. No. 

 45tU0, U.8.N.M.) ; calcareous-tufa, CaCO:;, after leaves, organic, Bear Spring, IJcaver 

 Head Canyon, Montana (Cat. No. 18618, U.S.N. M.). 



liy injiltration: Flint, SiOj, after echinus, organic, Gravesend, England (Cat. No. 

 82465, U.S.N.M.); silica, SiOi, after wood, organic, Greenwich, New Jersey (Cat. No. 

 81879, U.S.N.M.). 



Pseudomorphs by alteration include those cases in which there has 

 been a partial change of composition or structure and the secondary 

 mineral retains some of the constituents of the first. This alteration 

 may take i)lace. First, through paramorphism, or molecular rearrange- 

 ment. Second, by the loss or assumption, or both, of an ingredient. 

 Third, by a partial exchange of constituents. 



Ji.ramphs. 



I'aramorphs: Aragonite, OaCOg, after calcite, CaCO:i, Girgenti, Sicily (Cat. No. 

 46,527, IJ.S.N.M.); rutile, TlOj, after brookite, TiO., Magnet Cove, Arkansas. (Cat. 

 No. 50048, U.S.N.M.) 



Loss: Copper, Cu, after azurite, Cu:t(0H)a(C0:!)2, Copper Glance and Potosi mines, 

 Grant County, New Mexico. (Cat. No. 48678, U.S.N.M.) Azurite, Cu:i(OH),(CO:i)., 

 altering to malachite, Cu.2(0H)2C0:i, Copper Queen mine, Bisbee, Arizona. (Cat. 

 No. 48127, U.S.N.M.) 



Asaniiiption: Malachite, Cu..(OII):CO.,, after cuprite, CujO, Chessy, France. (Cat. 

 No. 82086, U.S.N.M.) 



Z/Oss and assumption: Galena, PbS, after pyromorphite (PbCl)Pb4(PO,)::, Bern- 

 kastle, Prussia. (Cat. No. 46173, U.S.N.M.) 



Exchanije of (■ousliturnis: Chlorite (Fe,Mg).:, (Al,Fe).2 Si40i.,. SHjO after garnet, 

 (Fe,Ca,Mg,Mn)3Al2Si;j0,2, Salida, Chaffee County, Colorado. (Cat. No. 81216, 

 U.S.N.M.) 



