1 64 General Notes. [February, 



in elasticity and cohesion. Among the optical characters of 

 minerals described are double refraction, phenomena of thin 

 plates, interference figures, optic axial divergence and method of 

 measurement, determination of the plane of polarization, circular 

 polarization, pleochrism, theoretical explanation of the characters 

 of uniaxial and biaxial crystals, etc. 



It is to be hoped that this work may be translated into English 

 for the benefit of the many students who feel the need of some 

 such advanced textbook. 



Mineralogical News. — It is stated that Mt. Mica, Maine, 

 has been purchased by a mining company and is being worked 

 for tourmaline, cassiterite and mica. This locality has yielded 

 a large number of interesting minerals, and has been especially 



famous for its beautifully colored tourmalines. Monazite has 



been found as minute tubular crystals, less than a millimeter in 

 diameter, at Nil St. Vincent, near Brussels. It occurs in a crystal- 

 line schist associated with rutile, tourmaline and zircon. The 



great beds of nitrate of soda which occur in the desert of Atacama, 

 Chili, have been derived from the decomposition of underlying fel- 

 spathic rocks. Vasite is an altered orthite found near Stock- 

 holm. It has been proved that the jade or nephrite of Siberia, 



like that of China, is a compact variety of tremolite. An 



excellent method of separating from one another the minerals 

 composing a rock, is to immerse the crushed rock in a very 

 dense liquid of known specific gravity. The specific gravity 

 of most of the minerals constituting rocks being between 2.2 

 and 3, it results that by preparing a liquid whose density may 

 be made to vary between those limits, the minerals may be readily 

 separated. Such a liquid is a solution of iodide of mercury in 

 iodide of potassium. A solution of borotungstate of sodium may 

 also be employed, the latter having a specifie gravity of about 3. 



Native lead has been found in Idaho. Fahlunite occurs at 



McKinney's Quarry, Germantown, Penna. Vermiculite occurs 



in Japan. It is in short six sided prisms of a brownish color. 

 When thrown upon hot charcoal, it expands longitudinally to 

 many times its original length, twisting and writhing like a 

 serpent, and is shown to passing travelers as a local wonder. It 

 is also used as a medicine. In many of its characters it is similar 



to the variety known as Philadelphite. Out of 200 columns of 



Basalt from the Giants Causeway, recently measured, there were 

 tetragons 3 per cent., pentagons 25 per cent., hexagons 50 per cent., 

 heptagons 1 9 per cent., octagons 2 per cent. Microscopic investi- 

 gations have revealed frequent impurities in the diamond. Organic 

 matter, carbon and bubbles of gas are common impurities. Quartz, 

 chlorite, pyrite and hematite have recently been found inclosed in 

 diamonds. Small crystals of topaz have also been seen within 



diamonds. Cossa has shown that all apatite contains phosphate 



of cerium, lanthanum and didymium united with phosphate of 



