7o6 CROSS, IDDINGS, PIRSSON, AND WASHINGTON 



crysts are tabular or prismatic, are relatively large to medium as 

 compared with the oikocryst. It is usually doxenic to xenoikic, but it 

 may be domoikic, or also perxenic. It may be magascopic or micros- 

 copic. The term has been employed only when the xenocrysts are 

 feldspar and the oikocrysts are pyroxene. 



Seriate fabrics.— These fabrics form the connecting links between 

 equigranular and hiatal, between even-grained and distinctly por- 

 phyritic or poikilitic. According to the relative amounts or abund- 

 ance of the larger or smaller crystals, they approach one or other 

 of these extremes of the series. Abundant large crystals with rela- 

 tively few of the smaller ones produce a fabric approaching equi- 

 granular, whereas relatively few large crystals with abundant smaller 

 ones produce a form of porphyritic fabrics, not necessarily hiatal, 

 but resembling hiatal porphyries. 



The first fabric would consist of relatively large crystals nearly, 

 or in fact, touching one another, with smaller and smaller crystals 

 between, or to some extent included in, the larger ones, giving rise 

 to the following fabrics: 

 (i) Seriate-inter serial — the rock might be called a seriate-inter- 



sertal aphyrite; an aphyrite being a nonporphyritic rock. 

 (2) Seriate- poikilitic — a seriate poikilite. 



The second kind of seriate fabric would be — 

 Seriate- porphyritic — the rock may be called a seriate porphyry. 



The multitude of variations in the relative sizes, shapes, and 

 proportions of crystals constituting rocks with seriate fabrics makes 

 it necessary to describe the fabric in detail in order to convey a correct 

 impression of it. The study of a hundred granites from different 

 localities will quickly convince one of the diversity of fabrics in rocks 

 with so-called "granitic" texture. They might all be described as 

 having multiform, seriate, aphyric fabric. But this would not 

 convey a definite picture of any one rock. In order to accomplish 

 this it is necessary to state the shapes of different kinds of crystals, 

 their relative sizes, and proportionate amounts. 



With such a definite picture before one, if possible in the form of 

 a diagram or photograph as well as in words, it is possible to compare 

 with it the fabric of another rock, which may be described as like 

 the first or as differing from it in certain particulars. If a certain 



