THE PROPERTIES OF MINERALS. 677 



CRYSTALLINE AGGREGATES. 



Many specimens of minerals occur in aggregates of imperfect crys- 

 tals; aceordinglj^ the remaining kinds of structure may be brought to- 

 gether under the head of crystalline aggregates. 



The individuals composing imperfectly crystalline masses may be: 

 In columns or fibers, in which case the structure is columnar; in thin 

 lamina-, plates, or leaves, giving rise to a lamellar structure; in grains, 

 producing a granular structure. Further, there are numerous irregular 

 and accidental groui)ings of the individuals composing the mass, giving 

 to it certain shapes, such as globular, botryoidal, reniform, dendritic, 

 etc., which are too numerous to allow of a specification here. These 

 indeterminate forms are grouped under the head of "imitative shapes.^ 

 Finally, the mass nuiy be entirely destitute of crystalline structure or 

 imitative shape. Such a mass is called amorphous. 



Examphs of Structure. 



Columnar. — Kyliudrite, Poopo, Bolivia. (Cat. No. 84156, U..S.N.M.) 



/'I'fcroMs.— Asbestus. Corsica. (Cat. No. 822.59, U.S.N.M.) 



Stellate.— 'f^tnhite, Wassous Blutf, Nova Scotia. (Cat. No. 83407, U.S.N.M.) 



Radiated. — Toiinnaliue in leiiidolite, Sau Diego, California. (Cat. No. 83434, 

 U.S.N.M.) 



Lamellar. — Glancophane, Cam}t de Praz, Aosta, Piedmont. (Cat. No. 84124, 

 U.S.N.M.) 



Straif/ht lamellar. — WoUastonite, Natural Bridjje, Lewis County, New York. (Cat. 

 No. 49698, U.S.N.M.) 



Lamellar foliated. — Talc, St. Lawrence County, New York. (Cat. No. 44867, 

 U.S.N.M.) 



LAimellar micaceous. — Margarito on emery, Chester, Massachusetts. (Cat. No. 13100, 

 U.S.N.M.) 



PheiiocrystaUiue. — Chrysolite, Webster, J.acksou County, North Carolina. (Cat. 

 No. 48521, U.S.N.M.) 



Cryptocrystalline. — Willemite Fraukline, Sussex County, New .Jersey. (Cat. No. 

 83615, U.S.N.M.) 



Amorphous. — Opal, Douglas County, Washington. (Cat. No. 83447, U.S.N.M.) 



Examples of imitative shape. 



Bofriioidal.—Ciicholoug, Lulling, Carinthia. (Cat. No. 82067, U.S.N.M.) 

 Mammillari/.—Malachito, Australia. (Cat. No. 82076, U.S.N.lVi.) 

 (rlohular.—F»ilome]ane. Freiberg, Saxony. (Cat. No. 46016, U.S.N.M.) 

 Com//oi(Z«7.— Aragonite, Dubuque, Iowa. (Cat. No. 82368, U.S.N.M.) 

 Arborescent. — Copper, Copper Falls, Michigan. (Cat. No. 12061, U.S.N.M.) 

 Dendritic. — Manganese dendrite, Gallatin County, Montana. (Cat. No. 46950, 



U.S.N.M.) 



lieticulated.—Chalcopyrite, Bristol, Connecticut. (Cat. No. 13162, U.S.N.M.) 

 Stalactitic.—Ciilcite, Kutztown, Pennsylvania. (Cat. No. 43126, U.S.N.M.) 

 Capillary. — Millerlte in calcite, Cement quarry, Milwaukee, Wisconsin. (Cat. No. 



45838, U.S.N.M.) 



Druay. — Quartz on chalcedony, California. (Cat. No. 17006, U.S.N.M.) 



