6GG REPORT OF NATIONAL MUSEUM, 1897. 



II. MAGNETISM SERIES. 



Magnetite, contains the magnetic element iron. Magnet Cove, Arkansas. (Cat. 

 No. 27291, U.S.N.M.) 



Pyrrbotite, contains the magnetic element iron. Gap mine, Lancaster Connty, 

 Pennsylvania. (Cat. No. 39391, U.S.N.M.) 



Hematite, contains the magnetic element iron. Mar(|uette, Michigan. (Cat. No. 

 18142, U.S.N.M.) 



Galena, nonmagnetic, contains the nonmagnetic clement lead. Joplin, Missouri. 

 (Cat. No. 18165, U.S.N.M.) 



Corundum, nonmagnetic, contains the nonmagnetic element aluminum. Powder 

 Spriugs, Cobb County, Georgia. (Cat. No. 46256, U.S.N.M.) 



Azurite, nonmagnetic, contains the nonmagnetic element cojiper. Copper Queen 

 mine, liisbee, Arizona. (Cat. No. 83753, U.S.N.M.) 



III. LUSTEK SEUIES. 



Galena, metallic, composed chiefly of metallic elements. Utah. (Cat. No. 18213, 

 U.S.N.M.) 



Pyrite, metallic, composed chiefly of metallic elements. Central, Colorado. (Cat. 

 No. 51364, U.S.N.M.) 



Stibnite, metallic, composed chiefly of metallic elements. Hill Grove, New South 

 Wales. (Cat. No. 82475, U.S.N.M.) 



Pyrrbotite, metallic, composed chiefly of metallic elements. Gap mine, Lancaster 

 Connty, Pennsylvania. (Cat. No. 39391, U.S.N.M. ) 



Albite, nonmetallic, composed chieily of nonmetallic elements. Amelia Court- 

 house, Virginia. (Cat. No. 48723, U.S.N.M.) 



Muscovite, nonmetallic, comi)osed chiefly of nonmetallic elements. Chester County, 

 Pennsylvania. (Cat. No. 83478, U.S.N.M., the Lea collection.) 



Magnesite, nonmetallic, composed chiefly of nonmetallic elements. Gilroy, Cali- 

 fornia. (Cat. No. 16070, U.S.N.M. ) 



II. PHYSICAL MINERALOGY. 

 A — PROPERTIES RELATING TO FORM OR MOLECULAR STRUCTURE. 



THE CRYSTAL. 



Substances which are chemically homogeneous, when they solidify 

 from a state of vapor, solution, or fusion, tend to assume certain regu- 

 lar forms as a result of mathematical symmetry in the action of cohe- 

 sive attraction. The forms jjroduced are regularly bounded solids, 

 called crystals. Crystals are bounded by plane surfaces, called i)lanes 

 or faces, symmetrically arranged with reference to and whose position 

 in a given crystal is related in some simple ratio to the relative lengths 

 of one or more diametral lines called axes. The angles of a crystal 

 are of tWo kinds, interfacial and solid. The interfacial angle is that 

 formed by the intersection of two crystal planes, and the line of such 

 an intersection is called an edge. The solid angle is that formed by 

 the intersection of three or more crystal faces. The angles or edges of 

 a crystal are often replaced by one or more planes. When an edge is 

 replaced by a single plane it is said to be truncated; a replacement by 

 two similar planes is a bevelment. Further, the corresi)ouding angles 



