Minerals from New Holland. 315 
produced. See Fig. 7. On some of 
the rhomboids, however, which do not 
. present any portion of the faces parallel 
with their axes, we may observe the 
small triangular planes which finally 
produce the six-sided pyramids. ‘The 
terminal primary planes P, are smooth 
al bright, while the elongate faces r, are curved and 
roughened by transverse strie. Sometimes the usual 
six-sided prisms, terminated by similar pyramids, have 
their alternate lateral solid angles replaced by small 
rhombic planes, inclining equally upon the sides of the 
prism, producing the quartz rhombiféere of Haüy. 
The sides are also striated parallel with their edges of 
combination with the faces of the pyramids. This au- 
thor ( Traité de Minéralogie, Tome Second, p. 413)de- 
scribes these rhombs as existing only on the alternate 
angles; but:in: the later works of Mohs, Beudant, 
and others, they are figured also upon. the interme- 
diate angles, being always represented as covering 
but a very small portion of the: acuminating pyramids. 
According to Phillips, the “ Bornholm Diamonds”’ 
afford the most perfect examples of this modification. 
Green Chalcedony and:,Heliotrope. — This first- 
mentioned mineral is of a deep serpentine green 
color. It breaks with a conchoidal fracture, disclos- 
ing, in the centre of the mass, blood red spots of jas- 
per, and thus constitutés the heliotrope. There are 
spots also of a lighter green, and bluish white chalce- 
dony, interspersed with the deeper ground, which, if 
polished, would render the specimens highly orna- 
mental in vignes. 
