Occurrence
Clinohedrite was first described by Penfield and Foote (175), from whose paper this description is chiefly taken. It was seen by them in a few specimens found on the dump of the Parker shaft (not the Trotter mine, as stated by Penfield and Foote) and was supposed to have come from a depth of about 1,000 feet, but the exact location in the mine and the form and geologic relations of the deposit are not known. This is the more unfortunate because in the specimens and closely associated with the clinohedrite were found the rare minerals hancockite, nasonite, glaucochroite, and roeblingite, of which only nasonite is known elsewhere. The many other minerals also found there indicate that the assemblage was formed under peculiar conditions, information regarding which would be of much interest.

The type specimen of clinohedrite in the Hancock collection is a group of lovely amethystine crystals lining a cavity an inch across in a mass of franklinite ore mixed with green willemite and hancockite. In other specimens veins of clinohedrite cut massive axinite and hancockite, and lamellar clinohedrite lines cavities and contains embedded prismatic crystals of clear-green willemite and also fills the interstices in a mixture of green willemite and glaucochroite.

Figure 158 Prismatic crystal of clinohedrite showing the forms a(100), b(010), h(320), m(110), m1(110), n(120), l(130), p(111), and u(531). Parker shaft.
	Figure 159 Crystal of clinohedrite showing the forms b(010), m(110), m1(110), d(150), l(130), e(101), p(111), q(111), r(331), s(551), t(771), k(311), u(531), and v(171), and w(151). Parker shaft. The crystal is viewed with the orthoaxis in front instead of in the usual position.
Figure 160 Doubly terminated crystal of clinohedrite showing the forms b(010), m(110), e(101), e1(101), p(111), q(111), q1(111), o(131), o1(131), r(331), s(551), t(771), u(531), g(511), and x(131). Parker shaft. The crystal is viewed with the orthoaxis in front instead of in the usual position.

In 1914 clinohedrite was identified by the author on two specimens from Franklin obtained for the Harvard collection by Mr. Cahn. There is little doubt that they came from the deeper levels at the north end of the ore body. In one of them short, stout crystals of clinohedrite (figure 161) are thickly implanted over several square inches of a surface of massive ore that contains vugs in which are crystals of hodgkinsonite and willemite. The clinohedrite crystals are white or faintly amethystine and are not more than a tenth of an inch in greatest dimension. Because of their habit and the pearly luster on the clinopinacoid they were at first mistaken for gypsum.

Figure 161 Stout prismatic crystal of clinohedrite showing the forms b(010), m(110), m1(110), e(101), p(111), and u(531). Parker shaft.

The other specimen shows a vein one-fifth of an inch thick in ore made up of franklinite and granular hodgkinsonite. The vein is drusy, containing fan-shaped clusters of white, opaque platy crystals of clinohedrite, strongly resembling barite or calcite, of the habit shown in figure 162, with pink crystals of hodgkinsonite and clear white calcite.

Figure 162 Projection on the clinopinacoid of a crystal of clinohedrite showing the forms b(010), m(110), e(101), p(111), q1(111), k1(311), x(131), and j(251). Parker shaft.

In 1928 in the mine at Franklin, on the 400-foot level in the north end, specimens were found that contained clinohedrite associated with several other species as described on page 81. The clinohedrite is fairly abundant in clusters of prismatic crystals lining cavities and intergrown with needles of larsenite. It is snow-white or glassy and transparent, with optical properties identical with those of the mineral from the occurrence first described. The prismatic habit is developed parallel to the zone containing the forms e, p, b, and p₁. These crystals are shown in figures 163 and 164 and are markedly different in habit from any others hitherto described.

Figure 163 Projection on the clinopinacoid of a crystal of clinohedrite showing the forms b(010), m(110), m1(110), n1(120), e(101), p(111), p1(111), and A(311). Franklin.
	Figure 164 Projection on the clinopinacoid of a crystal of clinohedrite showing the forms b(010), m1(110), n(120), n1(120), p(111), p1(111), q(111), t(771), A(311), and x1(131). Franklin.

The crystal shown in figure 165 came from another specimen in this lot. It is doubly terminated and shows the new form B(434).

Figure 165 Doubly terminated crystal of clinohedrite showing the forms a(100), m(110), m1(110), e(101), p(111), p1(111), q1(111), s(551), u(531), and B(434). Franklin.