472 II. 13. PATTON — THOMSONITE, MESOLITE, AND CHABAZITE 



monly labeled as from Aussig) show scalenohedral striations and also 

 similar forma and twinning, but lack the prism a. 



Other Zeolites 



analcite 



The other zeolites present may be dismissed with a very brief mention, 

 inasmuch as they have already received ample description. Next to 

 thomsonite analcite is the most abundant zeolite present. The milky 

 white variety is the most abundant, but clear glass} 7 crystals are not want- 

 ing. In size they vary from 1 millimeter up to %\ inches in diameter. 

 Specimens measuring 1 inch are common. They sometimes occur alone, 

 lining the cavities on all sides, but more frequently they lie on a coating 

 of chabazite or of thomsonite of types I and II. The form is the char- 

 acteristic trapezohedron 2 02 (211), sometimes with the edges running to 

 the center of the octant slightly truncated by the trisoctahedron f (332). 

 Its period of growth about corresponds with that of thomsonite, type 

 III, as it occurs sometimes beneath this variety, sometimes penetrated 

 by its needles. In one case a few minute crystals of analcite were ob- 

 served growing upon the very delicate hairlike fibers of mesolite. This 

 would indicate that analcite occurs here in two generations. 



APOPHYLLITE 



Apophyllite is very sparingly represented by snow-white opaque 

 crystals, with the characteristic steep pyramid and indirect prism. It 

 occurs in crystals from a quarter to half an inch in length ; is always 

 associated with analcite and always imbedded in and therefore older 

 than that mineral. 



STILBITE AND LA UMONTITE 



Stilbite and laumontite occur, as described b}^ Cross and Hillebrand, 

 forming the bedded floor of many cavities, and also as larger and dis- 

 tinctly crystallized specimens growing freely on the upper surface of the 

 bedded floors. A second generation of both of these minerals has been 

 noted in a few, cases. In one case snow-white ciystals of laumontite 

 showing the customary square prism and steep orthodome occur, grow- 

 ing on a quarter-inch layer of thomsonite, which forms the uppermost 

 deposit of the bedded floor. These laumontite crystals measure from 5 

 to 10 millimeters in length and half a millimeter or more in thickness. 

 The position of this thomsonite layer with reference to the order of 



