252 Account of some new Vesuvian Minerals. 
solves with extreme difficulty, and forms a brown opaque 
enamel. With the phosphoric salts it dissolves with equal 
difficulty, and forms a globule, translucent under the flame, 
but changing to a brown opaque enamel on cooling, owing 
to a deposit of silex. 
Varieties. 1. It occurs of the primitive form. (see figure 
188.) 2. Peri-hexahedral. (fig. 189.) 3. Peri-octahedral. 
(fig. 180.) a. The same shortened. (fig. 191.) 4. Peri-do- 
decahedra}. (fig. 192.) a. The same shortened. (fig. 193.) 
5. Peri-dioctahedral. (fig. 194.) 
Also cylindrical, and in a translucent vitreous mass of # 
greenish yellow color. ; 
Dimensions. : The crystals of the primitive variety do not 
exceed three millimetres in length, at the base, and one and 
a half in height. Bae hexagonal variety is larger, having 
nm ; 
a length of fiftee and a height of seven. 
i ao inclining, slightly to yellowish, or greenish 
Localit 
: y- The humboldite occurs in aggregate; Viz: 
eas In an aggregate composed of particles of zurlite, yel- 
wish and amorphous, and of pyroxene, also amorphous, and 
greenish brown, the particles adhering forcibly, and in some 
— epeoring united by fusion. The mass, at times, a5- 
aaa Peisk : nt aspects of porous and fine grained, and 
