342 
[B.N.F.C. 
( 2 ). The Zeolitic and Calcitic Layer, deposited im- 
mediately on the surface of the hullite, consists of a 
thin layer, occasionally of fibrous zeolites, but gener- 
ally composed of calcite. The usual thickness of 
this layer is about one-sixteenth to one-eighth of an 
inch, and it is mostly much weathered. The 
zeolitic parts of this layer appear to consist chiefly 
of natrolite, and occasionally this passes into 
analcime. Small crystals of chabazite are also to 
be found in this portion of the vein. The zeolites 
and calcite are rarely found together, but when they 
occur thus, the former have been deposited upon 
the latter. The thin layer of calcite frequently 
develops sporadic crystals of that mineral to % 
of an inch in length. 
{3). The Chalcedonic Layer, coating the second layer, 
and sometimes entirely filling the central portion of 
the vein. After a single layer of chalcedony had 
been deposited, the large sporadic crystals of calcite 
again appeared here and there on its surface. 
These crystals in turn became enveloped by a 
second, and by succeeding layers of the chalcedony, 
and the finest examples of spherical crystalline 
growth may be found in the latter. In such in- 
stances, there is often in the chalcedony immediately 
investing the calcite crystals, a zone of white, 
opaque, jaspery material, containing calcareous and 
zeolitic matter. 
The Carnmoney chalcedony exhibits all the typical 
structures of that mineral. In colour it varies from bluish- 
white to bluish-grey, the latter being more translucent than the 
whiter varieties. A beautiful translucent specimen, with typical 
reniform structure, was found to have a specific gravity of 
2.582. A section through the reniform chalcedony shows very 
well its fibrous and spherically-crystalline arrangement. The 
chalcedony is almost entirely composed of these ‘radiate- 
