66 A. S. EaJde — Erionite. a new Zeolite. 



Art. VI. — Erionite, a new Zeolite / by Arthur S. Eakle. 



The mineral described in the present paper occurs in a 

 rhyolite-tuff from Durkee, Oregon, and was discovered and 

 presented to the museum for identification by Mr. E. Porter 

 Emerson. The tuff consists of a dull gray, amorphous ground- 

 mass containing numerous patches of light brown, pitchstone- 

 like material, fresh sanidine and plagioclase crystals, with an 

 occasional dark silicate altered to chlorite. Large masses of 

 opal fill the cavities. This opal is mostly of the milky and 

 hyalitic kinds, yet often grades into a beautiful precious variety, 

 showing a rich play of colors and forming excellent gem ma- 

 terial. 



The zeolite occurs as very fine threads, having a snow-white 

 color and pearly luster. These threads resemble fine woolly 

 hairs, having the same curly nature and soft feel. They occur, 

 sometimes as white tufts firmly adhering to a solid base of 

 milky opal, resembling a filamentous growth of the opal, and 

 sometimes as compactly matted fibers filling the rock fissures. 

 In some of the specimens, the filaments are encrusted with a 

 thin shell of white opal, indicating that the opal was subse- 

 quently formed from the zeolite. 



The mineral fuses easily and quietly in the Bunsen flame, to 

 a clear colorless glass. Heated in a closed tube, the fibers 

 darken slightly, emit a burnt odor, and give off much water 

 which reacts strongly alkaline. The tuff also shows this alka- 

 line reaction, so it is evident that organic matter of some sort 

 is present in the rock. The organic substance in the zeolite 

 must be a part of its constitution and not a contamination of 

 any hydroscopic water, since it cannot be eliminated by long 

 boiling in water or acids. 



The weight of the fibers fluctuates materially from the influ- 

 ence of the air, making correct weighings difficult. The loss 

 over sulphuric acid is water of crystallization, as evidenced by 

 the rapidity with which such loss is regained on exposure. 

 Two-thirds of a gram of the material which had been exposed 

 to the air of the laboratory for two months, was weighed in a 

 platinum crucible and placed in a desiccator for a week. At 

 the end of this period the loss was 6*95 per cent ; in one hour, 

 on the balance pan, one-half of this loss was regained ; in two 

 and a half hours, the fibers reached their original weight ; in 

 four hours, their weight became stationary and exceeded the 

 original weight by 60 milligrams, although the weighings were 

 made in a warm dry room and the balance case contained a 

 beaker of strong sulphuric acid. In the air bath at 110° C, 



