STRONTIA. 



213 



Fig. 52. 



Fig. 53. 



Fig. 54. 



carbonate of strontia, containing only a very small admixture of carbonate of lime and oxide 

 of iron. In the vicinity of the court-house, strontianite also occurs in fibrous masses, im- 

 planted upon a dark blue calcareous spar. Some of these fibres are nearly two inches in 

 length, and resemble certain varieties of arragonite. 



Various crystalline forms have also been noticed at this 

 locality. Of these. Fig. 52, Fig. 53, and Fig. 54, are intro- 

 duced from Prof. Shepard's paper on the Strontianite of Scho- 

 harie.* P on a 120° (Y ; a on a 120° 0' ; o on o 160°. 



Fig. 53 represents a compound form, commonly called a V 

 crystal. " The face of composition is apparently parallel with 

 the vertical edges between c and c (Fig. 52). The individuals 

 project beyond the face of composition only on one side ; but 

 the composition is often represented in parallel laminas." 



" Another form is represented by Fig. 54, though the planes 

 c c are rarely very distinct. They are an inch in length (in 

 the direction of the edge between a and a), and nearly half an 

 inch in thickness. Colour bluish or reddish grey ; translucent. 

 The surface P is streaked parallel with its edge of combina- 

 tion with 0." 



The Emmonsite of Dr. Thomson, is certainly nothing more 

 than a mechanical mixture of carbonate of strontian and carbo- 

 nate of lime. The composition is stated to be as follows : 



Carbonate of strontia, . 82.69 



Carbonate of lime, _ 12.50 



Peroxide of iron, . 1 .00 



Zeolite, 3.79t 



The remarks made in regard to the mixtures of sulphate of barytes and carbonate of lime 

 (page 207), are equally applicable in this case. The chemical composition alone cannot be 

 relied on as a ground of specific distinction. 



B ARYSTRONTI ANITE . 



[From its containing both baryta and strontia.] 



Barystrontianite. Ckaveland and Phillips. — Stromnite. ThoTnson and Shepard. — Appendix to Strontianite. 



BeudarU. — Baryto-Carbonate of Strontia. 



Description. Colour greyish white, passing into yellowish white. It occurs massive, ra- 

 diated, or composed of small plates or radii somewhat diverging. Lustre shining, inclining 



• Ammcan Journal of Science, XXVII. 363. 



t lb. XXXI. 171. 



