1 882.] Mineralogy. 423 



conclusion has been reached by Mallard that the elementary form 

 of titanic acid is monoclinic with tetragonal habit, and that each of 

 those minerals represent merely different twinning arrangements 

 ofthe same elementary form. Apatite, tourmaline, emerald and 

 corundum are examples of pseudo-hexagonal minerals, formed by 

 the twinning of orthorhombic crystals, while other examples 

 might be given in the remaining systems. 



Interesting as are the conclusions here reviewed, it is to be 

 remembered that other and more simple explanations of these 

 " optical anomalies " have been offered, which do less violence to 

 our crystallographic ideas and are perhaps nearer the truth. 

 Most of the mineralogists of Germany are opposed to this twin- 

 ning hypothesis, and hold that all the optical phenomena in ques- 

 tion can be explained by irregularities of internal tension in the 

 crystal. The fact, recently discovered, that when amorphous 

 gelatine is cast in the form of a crystal, it frequently shows, after 

 drying, optical phenomena identical with those under discussion 

 (e. g., analcite), lends great weight to this latter and more simple 

 hypothesis. 



Hieratite, a New* Mineral. — At the February meeting of the 

 Mineralogical Society of France, M. Cossa described a new min- 

 eral which occurs in microscopic crystals in volcanic tufa 

 around the fumaroles of the crater of the Island of Vulcano 

 (one of the Lipari islands). The minute crystals dissolve in 

 boiling water to form an acid solution, from which there soon 

 separates a gelatinous substance which, after desiccation, becomes 

 a mass of transparent isometric crvstals, of which the predomi- 

 nant form is the cube mod fi I by the octahedron. The compo- 

 sition ofthe crystals was found to be that of a fluosilicate of po- 

 tassium 2KFl,SiFl 4 The name, Hieratite, is suggested by the 

 Greek name ofthe island, c h P d. 



Hieratite occurs abundantly in the stalactitic concretions which 

 cement the tufa and decomposed lava, and is associated with 

 selensulphur, realgar, mirabilite, glauberite, sassolite ; the alums 

 of potassium, caesium and rubidium ; and the soluble salts of arse- 

 n 'c, iron, thallium, zinc, tin, bismuth, lead and copper. 



Attention is called to the abundant occurrence of a compound 

 of tin soluble in water, possibly an alkaline fiuostannate, and to a 

 soluble bismuth salt, both of which may be new. 



—Prof. G. A. Konig 1 has identified 

 in Amelia Co., Va , thus adding 

 »«» another rare mineral to the list already reported from that 

 locality. It occurs in masses, some of which are from fifteen to 

 twenty pounds in weight. Two varieties were noticed, one hav- 

 m S an amber or brown color, a straw-colored powder anJ a spe- 



1 Proc A. N. S., Phila., Jan. 24, 1882. 



