478 Ihe American Naturalist. [Jull e, 



and are pronounced by him to be aggregates of zoisite, epidote, sericite 

 and chlorite in a mass of basic plagioclase. In other words, huronite 

 is a saussuritized plagioclase. Descriptions of a number of dyke rocks 

 containing « huronite ' are given by this author. 



Bauer 7 describes a number of specimens of snow-white, lilac and 

 emerald-green jadeite from Thibet and upper Burmah. One of the 

 green varieties is cut by little veins of nepheline, containing plates of 

 basic plagioclase and little bundles of a monoclinic augite (jadeite) 

 with the same properities as that which constitutes the mass of the 

 jadeite. The rock, according to the author, is made up of this augite 

 and nepheline, the latter mineral acting as a groundmass. The veins 

 are those portions of the rock in which the augite is in very small 

 quantity. In other specimens nepheline occurs in small quantity, and 

 plagioclase is abundant. His conclusion is that the rock is a jadeite- 

 plagioclose-nepheline rock in which locally the one or the other compo- 

 nent is most prominent. If the rock is, as the author supposes, a crys- 

 talline schist, the occurrence of nepheline in it is of extreme interest. 



In a second article the same author 8 describes a serpentine from the 

 jadeite mines at Tauraan. It is composed of olivine, picrolite, chryso- 

 lite, webskyite and a few other accessories in an albite-hornblende 

 matrix, consisting of an aggregate of single individuals of untwinned 

 albite, in the midst of which lie brown and gray hornblendes sur- 

 rounded by zones of a bright green variety of the same mineral. 

 Between this zone and the albite there is a fringe of green augite nee- 

 dles. The rocks associated with the jadeite and the serpentine are also 

 described. Among them is a glaucophane-hornblende-schist. All the 

 rocks exhibit the effects of pressure. 



In a very short note Beck 9 calls attention to the fact that the mole- 

 cular volume of dynamically metamorphosed rocks, i. e., of the min- 

 erals composing these rocks— is less than that of the original rocks 

 from which they are derived. For instance, a mixture of plagioclase, 

 orthoclase and water in the proportion to form albite, zoisite, muscovite 

 and quartz has a molecular volume of 547.1, while the corresponding 

 mixture of albite, zoisite, etc., has a volume of 462.5, 



7 Neues Jahrb. f. Mm., etc., 1896, I, p. 85. 



8 Record of Geol. Survey of India, XXVIII, 3, 1895, p. 91. 



9 Kais. Ak. V. ton* Clag8> Jan ; 1896 



