460 RECORD OF SCIENCE FOR 188G. 



in the place of the potassium. The name has reference to the high 

 percentage of the last-named element. 



Lucasite. — Another memberof the large group of hydrated micas called 

 vermiculites. It is described by T. M. Chatard, and named after Dr. 

 H. S. Lucas, who has been connected with the emery industry of this 

 country. It was found with corundum at Corundum Hill, Macon County, 

 !North Carolina. The physical characters are like the others of the 

 group. Of the 10.76 per cent, of water contained, 3.78 went off at 110° 

 C, and G.98 at a red heat (blast lamp). An analysis (mean of two) of the 

 substance, dried at 1 10°, gave : 



The ratio of silica to bases to water is 7 : G : 2. 



Mursinskite. — Named after the locality by Kokscharow on the basis of 

 a crystallographic study of two small crystals found thirty-two years 

 ago at the beryl locality at Alabaschka, near Mursinsk, Ural. It has 

 not been possible since their discovery to obtain additional material. 

 The crystals occurred imbedded in the beryl. They belong to the tetrag- 

 onal system and show one pyramid prominently, with two subordinate 

 of the other series, and several zirconoids. The terminal and basal 

 angles of the fundamental pyramid are respectively 127° 32' and 77° 

 23^', corresponding with a vertical axis, c=0.5G64I. The color is white 

 to honey-yellow, transparent to semi-transparent. Hardness = 5 to G, 

 specific gravity uncertain, though a trial on the crystal weighing .01 

 gram gave P. v. Nikolajew 4.149. Nothing is known of the chemical 

 composition. Kokscharow calls attention to the fact that the pyramidal 

 angle corresponds nearly with the pyramid ^P-jd of vesuviaiiite, but 

 there appears to be no further relation between the species. 



Ptilolite. — A new zeolitic mineral described by Cross and Eakins. The 

 name is from -rtAov, doiai, in allusion to the delicate fibrous nature of the 

 mineral. It is found in cavities of a vesicular augite andesite, found in 

 fragments in the conglomerate beds of Green and Table Mountains, 

 Jefferson County, Colorado. These cavities are in some cases filled with 

 chalcedony and quartz, or sometimes only lined with chalcedony, and 

 upon this is deposited the ptilolite in delicate white tufts or spongy 

 masses, consisting of short hair-like needles loosely aggregated. They 

 appear to have parallel extinction. An analysis by Eakins gave: 



: 99.90 



This corresponds to the formula EAl2Siio024+5n20 or RO. AI2O3. 10 

 Si02+51l20, requiring, when R=Ca : K : Na= 



SiOj AljOj CaO KjO Na20 H2O 



69.86 11.87 4.04 2.95 0.80 10.48 = 100 



The mineral is remarkable for its high percentage of silica. 



