122 C. 11. Warren — Mineralogical Notes. 



6. 7. 8. 



A crystal obtained from Mr. L. B. Merrill of Paris, Maine, 

 and now in the Brush collection at New Haven, has the habit 

 shown in fig. 6. This crystal is apparently not twinned. Its 

 diameter is about 18 mm and specific gravity 7*67. 



Fig. 7 represents a crystal belonging to Mr. T. F. Lamb of 

 Portland, Me. This crystal is a twin, measuring about 2 cm in 

 diameter and having a specific gravity of 7*68. The crystal 

 faces are rough, and they show, when examined with a lens, a 

 superficial growth of minute prismatic crystals in twin posi- 

 tion, and crossing at angles of about 60°. The surface of the 

 crystal resembles some of the brookite crystals from Magnet 

 Cove, Arkansas, with a growth of rutile crystals in twin posi- 

 tion upon their surface. 



Fig. 8 represents a simple and almost ideally symmetrical 

 crystal, about 5 mm in diameter and with a specific gravity of 

 7*87, loaned by Mr. J. S. Towne of Brunswick, Me. 



Fig. 9 represents a very symmetrical twin 

 crystal also loaned by Mr. Towne. It has a 

 length of 2 cm , a breadth of l cm , and the spe- 

 cific gravity is 7*66. 



The high specific gravity of these tapiolite 

 crystals indicates that they are essentially 

 tantalates and contain very little niobium, 

 as has also been proved by qualitative chem- 

 ical tests. They contain iron as the base, and 

 give only a very slight reaction for manga- 

 nese. 

 The measurements given in columns I, II and III were 

 obtained from the crystals represented by fig. 6, 8 and 9 respec- 

 tivelv, and the calculated values are obtained from the measure- 



ment given by Nordenskiold^>A^, 



I. n. 



infill 



p/^p, over 



twinning plane, 123° W 122 c 

 100/Ull 61 



11CW 11 47 



101 yy 111 28 25 28 26£ 



100/^301 27 10 27 12 



lll/sl33 18 3 



111 a 111 = 84° 52'. 



III. 



r 



Calculated. 

 56°59f 



30| 

 34" 



01 

 47 



26^ 



123 



61 



47 

 28 

 27 

 18 



30 



34 



29f 



29 



14 



