C. H. Warren — Miner alogical JVotes. 121 



The high percentage of water and alumina, and low percent- 

 ages of alkalies, probably indicate the presence of cookeite, 

 which has been observed as a secondary mineral on other speci- 

 mens from the locality. Careful tests were made for beryllium 

 with negative results. 



3. Supposed JPseudomorphs after Topaz from Greenwood, Maine. 



In connection with the pseuclomorphs just described, there 

 occur other pseudomorphs of quartz after a prismatic, and 

 probably an orthorhombic mineral. The crystals are prisms 

 about 4 inches in length, having an angle about like the prism 

 m, 110, of topaz, and are terminated by basal planes. It 

 seems most probable that they are pseudomorphs after topaz, 

 but the original material has been wholly removed, and the 

 crystals now present the appearance of a shell of quartz, with 

 the points of innumerable crystals projecting outward, while 

 within they are cavernous, and the sides of the cavities are 

 lined with small quartz crystals, and rounded prominences of 

 cookeite. 



4. Crystallized Tapiolite from Topsham, Maine. 



In a recent article by Brogger* it has been shown that the 

 isomorphous molecules KXb a 6 and BTa 2 6 (R=Feand Mn)are 

 also dimorphous, there being the orthorhombic minerals colum- 

 bite RNb 2 6 and tantalite ETa 2 6 and corresponding to them 

 tetragonal species mossite and tapiolite. It was moreover shown 

 that the mineral skogbolite from Tammela, Finnland, described 

 by Nordenskioldf as orthorhombic, is identical with the tapiolite 

 from Tammela, also described by Nordenskiold,J the apparently 

 orthorhombic habit of the skogbolite resulting from a twinning 

 of a tetragonal crystal about a pyramid of the second order 101, 

 and an extension of some of the pyramidal faces into a pris- 

 matic form. Crystals of the tetragonal mineral rutile with an 

 apparently orthorhombic habit like that of tapiolite, and due to 

 a similar twinning, have been described by Pirsson § and 

 Miklucho Maclayl 



The tapiolite crystals to be described here are from the feld- 

 spar quarries of Topsham, Maine, and the following forms have 

 been observed on them : 



a, 100 e, 101 p, 111 



m, 110 s, 201 x, 133 



* Uber den Mossit and uber das Krystallsystem des Tantalit (Skogbolit) aus 

 Finnland, Yidenskabsselskabets Skrifter, I Mathematisk-natur Klasse, 1897, 

 No. 7. Kristiania. 



T Beskr. Finn. Min.. 30. 1S55. % Of v. Ak. Stockh., xx, 4.4.5, 1863. 



§ Am. J. So., xli, 249, 1891. || Jb. Min., ii, 88, 1885. 



Am. Jour. Sci.— Fourth Series, Vol. YI, No. 32. — August, 189S. 

 9 



