90 : Properties of Minerals. 
(b) Malleable—When slices may be cut off, and — 
these slices will flatten out under the hammer. 
(c) Sectile—When thin slices may be cut off with 
a knife. All malleable minerals are sectile. 
(d) Flexible—When minerals will bend and re- 
main bent after the bending force is removed. 
(e) Hlastic—When after being bent it will spring 
back to its original position. 
EIGHTH PROPERTY. 
ORYSTALLINE SYSTEM. 
Six systems of crystallization are recognizable 
among minerals, and these occur under an indefinite 
number of geometrical forms, but the system to which 
the crystal belongs is indicated by its mathematical 
symmetry, and in any case will be found to belong to 
one of the following siz fundamental systems: 
I. Isometric, or the cube, in which the three 
axes are rectangular in intersection, and equal. 
II. TETRAGONAL, or the right prism with square 
bases, in which the three axes are rectangular in inter- 
section ; the two lateral axes equal, and unequal to the 
vertical. 
III. orrHorHomsic, or the right rectangular 
prism, including also the right prism with equilateral 
rhombic bases, in which the three axes are rectangular 
in intersection, and unequal. 
IV. MoNnocuiInic, or the oblique prism with rect- 
angular bases, in which there are only one oblique in- 
clination out of the three made by the intersecting axes, 
and the three axes are unequal. 
V. TRICLINIC, or the oblique prism with rhombic 
bases, in which all the axes are obliquely inclined to one 
another, and unequal. 
