The first well-established evidence of diopside at Franklin is furnished by
analysis 1, above, made by L. H. Bauer,
of the New Jersey Zinc Company. The material, which is associated with franklinite,
is known locally as "white schefferite" and yields a ratio near
that of diopside with a little manganese in place of some of the magnesium.
The physical properties of this material, as determined by Berman, are as
follows: It has a basal parting and shows polysynthetic twinning on the base.
It is colorless and nonpleochroic; optically biaxial and positive; 2V
= 60° ±1°, r > v (weak); Z /\
c = 37° ±l° ; Y = b; a
= 1.673, b = 1.680, and g
= 1.700, all ±0.003.
Diopside and some of its subvarieties are named in all the older lists of Franklin
minerals, and many specimens so labeled were seen in the older collections. On careful
examination all proved to be either leucaugite, tremolite, or edenite. A specimen from
Sterling Hill, in the Roebling collection, proved, however, to be a pseudomorph of tremolite after a pyroxene of diopside
habit, and the original may well have been diopside.
Pyrallolite, which was listed by Robinson (22) and by Alger (39), is a talcose
pseudomorph after pyroxene.
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