The
attempt to make this crystal combination a habit of titanite is not
successful and leads to very improbable results, while all of its
properties so far determined consistently fit into the orthorhombic
scheme. It may be noted here that under the microscope its most marked
divergence from titanite is its inferior cleavage and straight
extinction wherever cleavage cracks are observable.
This
mineral may contain some other elements not shown in the preliminary
microchemical tests, but it may also be a dimorphous form of titanite,
or an orthorhombic end member of an isomorphous series.
The
name is taken from the ridge (primarily anticlinal component) of the
Diablo range on which the mineral occurs. The ridge received its name
from the prominent Joaquin rocks—a landmark of the region.30 It also borders the great San Joaquin valley.
Joaquinite
is found enclosed in the natrolite, both at the edge of the veinlets
and touching the wall rock, and also in the central portion of the
vein. It is also found enclosed in the neptunite and seems especially
to occur in those parts of the deposit rich in neptunite. Both the
natrolite and neptunite are molded about it xenomorphically.
a" See further Arnold and Anderson, Bull. JJ. S. Geol. Survey, No. 35" (1908), 13.
