Penfield — Chemical Composition of Hamlinite. 313 



Art. XXXVI. — On the Chemical Composition of Hamlinite 

 and its Occurrence with Bertrandite at Oxford County^ 



Maine ; by S. L. Penfield. 



In the summer of 1890, Mr. W. E. Hidden and the author 

 published a short description of a rhombohedral phosphate 

 occurring with the rare minerals herderite and bertrandite at 

 Stoneham, Maine. Only a single specimen, showing a few 

 minute crystals, was ever found at the locality, and the inves- 

 tigation was therefore incomplete, being confined to determina- 

 tions of the crystallization and physical properties and the 

 identification of phosphorus, aluminium, fluorine and water, 

 while from its association it was supposed that it would also 

 contain beryllium. 



The mineral was named hamlinite in honor of Augustus C. 

 Hamlin of Bangor, Maine, who has always taken a keen interest 

 in collecting and studying the minerals of his State and espe- 

 cially the beautiful tourmalines from Mt. Mica and vicinity. 

 As stated in the original article, the incomplete description 

 was published for the purpose of calling attention to a mineral 

 which would probably prove to be interesting, and also in 

 hopes that others would be led to look for the mineral and find 

 it. This hope has not been in vain, for Mr. Lazard Cahn of 

 New York had the good fortune to discover among a suite of 

 minerals from Oxford County, Maine, some specimens showing 

 rhombohedral crystals of a mineral, unknown to him, which he 

 gave to the author, suggesting that they might prove to be the 

 rare mineral hamlinite. It is hoped that additional informa- 

 tion may be obtained concerning the exact locality at which 

 the mineral is found, so that a supply of specimens may 

 become available for distribution. The mineral was readily 

 identified as hamlinite by its rhombohedral crystallization, basal 

 cleavage, positive double refraction, and blowpipe reactions. 



The crystals are implanted upon feldspar 

 and muscovite and are associated, like the ' 



ones from Stoneham, with apatite, herderite /[^\ 



and rarely bertrandite. The crystals present / / /\ 



two prominent habits: One a combination of / >' / \ 

 the rhombohedrons r, 1011 and f 0221, de- //T"\ / / \ 

 veloped as shown in the accompanying figure. / / H\--~./ / 

 On these crystals there are occasionally small V J /-^/ 

 basal planes and slight horizontal striations \ '/ /-U 

 on the rhombohedral faces near their junc- \ / / 



ture with the base. The other habit is essen- \// 



tially a combination of the hexagonal prism 

 of the first order, 1010, with the base, but, owing to a vicinal 



