398 



F. A. Genth — Contributions to Mineralogy : 



particles, the largest of about 10 mm diameter, disseminated 

 through a mixture of feldspar and zeolites, and associated with 

 segirite, astrophyllite, titanite, etc. On account of its scarcity, 

 the material, though selected with care and apparently free from 

 4. admixtures, was not of uniform color, some particles 

 being of a deep rose color, while others were of a 

 much paler shade. It is not impossible that the lat- 

 ter have already suffered a partial alteration. 



3. Ox Titanite feom Magnet Cove, Ark. 



One of the rarer minerals of Magnet Cove is 

 titanite. It occurs, associated with segirite, ortho- 

 clase (or microcline) elaeolite, one or two zeolites, 

 eudialyte and others in small pale brownish yellow 

 or brown crystals. Sp. gr. = 3*457. 



The crystals are very simple and show a combina- 

 tion of the two forms m, 110, I and w, 111,-1, 

 as in figure 4. The faces gave very poor reflec- 

 tions, so that only approximate measurements could 

 be made. 

 The analysis gave : 





/ "** \ 



m 



\m 



\ 



,-j. 



[-- 







.' / 



\ 



\/ 



Ignition _ 





— 0-5 7 



SiO a 





30-84 



TiO 





39*35 



FeO~ 





0-73 



Mo-0 





trace 



CaO 





28-26 





4. Monticellite. 







9975 



Among the specimens from Magnet Cove, Ark, sent to me 

 for identification by Messrs. Geo. L. English & Co., I observed 

 the very rare species Monticellite. It is found in crystals and 

 crystalline grains in a coarse-grained calcite, the individual 

 grains of which are from 2 to 15 mm in diameter, and is asso- 

 ciated with small crystals of magnetite, rarely over 3 mm in size 

 and apatite, in microscopic colorless hexagonal prisms, but 

 generally in crystalline radiating masses sometimes over 10 mm 

 in diameter. Mr. L. Y. Pirsson has very kindly examined the 

 crystals and gives in the following the results of his observa- 

 tions : 



The crystals are not well adapted for accurate measurement^ 

 the faces being roughened in some places and in others lacking 

 the polish on the crystal planes. A few faces gave moderately 

 good reflections and on others by using the o ocular of Websky, 

 enough light could be condensed to give in a number of cases, 



