Pen field and Foote — Clinohedrite. 289 



Aet. XXXIX. — On Clinohedrite, a new mineral from Frank- 

 lin, JV. J. ; by S. L. Penfield and H. W. Foote. 



The mineral that is to be described in the present paper was 

 first brought to our notice in the autumn of 1896 by Mr. 

 Frank L. JSTason of West Haven, Conn., who sent a few speci- 

 mens of it to the Mineralogical Laboratory of the Sheffield 

 Scientific School for identification. When informed that the 

 mineral was a new species Mr. Nason visited the locality for 

 the special purpose of obtaining more material, but so little 

 was found that it seemed best to postpone the investigation 

 until more could be secured. About a year later Mr. E. P. 

 Hancock of Burlington, 1ST. J., sent some Franklin minerals to 

 our laboratory for identification, among them specimens of the 

 new mineral, and on learning the nature of the material he 

 took a keen interest in having it investigated, generously plac- 

 ing at our disposal for that purpose the few specimens he had 

 collected. A short time later Mr. W. F. Ferrier of Ottawa, 

 Canada, also called our attention to an exceptionally fine speci- 

 men of the mineral, which he had had the good fortune to 

 find at the locality. 



The specimens were all obtained from the dump of one of the 

 new shafts of the Trotter mine, and are supposed to have come 

 from a depth of about one thousand feet. The mineral is asso- 

 ciated with transparent prisms of green willemite, a massive 

 variety of brown garnet, phlogopite mica, small yellow crystals 

 of axinite, dull crystals of datolite, and a reddish-brown min- 

 eral, occurring in slender prismatic crystals, which is now being 

 investigated, and proves to be a new silicate containing lead, 

 iron and calcium as essential constituents. 



The crystallization is monoclinic, and the crystals are espe- 

 cially interesting as they belong to that division of the mono- 

 clinic system characterized by a plane of symmetry, but not an 

 axis of symmetry, or to the class of crystals called by Groth* 

 the " domatische KlasseP No form in this class consists of 

 more than two faces, and the pinacoid b, 010, is the only one 

 where the faces are parallel. The prevalence of forms without 

 parallel faces gives to the crystals a peculiar inclined faced 

 character or appearance, which has suggested the name of the 

 mineral, clinohedrite (/cXiveiv, incline, and e8pa, face). Very 

 few examples of this kind of symmetry have been observed 

 among mineral substances, the best being some crystals of 

 pyroxene described by Williams,f but pyroxene generally 



* Physikalische Krystallographie, 3 Anflage, p. 356, 1895. 

 f This Journal, xxxviii, p. 115, 1889. 



Am. Jour. Sol — Fourth Series, Vol. Y, No. 28.— April, 1898. 

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