PHYSICAL PROPERTIES 



209 



Powdery. Is when the fine individuals are easily parted and 

 break down under slight pressure. 



Lamellar. Is when the individuals are flattened and in paral- 

 lel posit ion and easily parting, as some talc. Foliated is an equiva- 

 lent term, only the laminae are thicker. 



Radiated. Formed of individual crystals, usually acicular, 

 which radiate from a point, the nucleus of crystallization, like the 

 sticks of a fan. Sometimes termed fan-shaped, as calamine or 

 wavdlitc, Fig. 382. 



Reticulate. Individual prismatic crystals arranged like lat- 

 ticework, with definite twinning angles, as the rutile from Tavetsch, 



Fio. 383. Reticulate Rutile, enlarged. Tavetsch, Switzerland. 



Switzerland, Fig. 383, or irregularly matted, as the cerussite from 

 Cornwall, England. 



Dendritic. Branching forms deposited from solutions, in 

 cleavage cracks and rock fissures, as pyrolusite or metallic copper, 

 Fig. 384. 



Wiry. Like wire, usually native metals, as silver or gold, also 

 in sheets or leafy. 



Nuggets. Are irregular rounded or rolled lumps, usually applied 

 to the precious metals, as gold, silver, or platinum, Fig. 385. 



Nodular. Applies to rounded individual masses of minerals; 

 as the rounded balls of pyrite occurring in some clays, Fig. 386. 



