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b) Hypautomorphic granular, in which some of the crystals, or 

 parts of some crystals, are automorphic, while others are xeno- 

 morphic. 



c) Panautomorphic granular, in which all the crystals possess 

 their proper forms more or less perfectly. Of course absolute 

 automorphism cannot exist in a compact, continuous rock. The 

 precise character of this fabric depends on the kinds of minerals 

 present and on their particular habit. It is, therefore, different 

 in rocks of different compositions so far as observed. 



Tabular or prismatic fabric. — There is further modification of 

 it in case the shapes of some of the minerals are tabular or pris- 

 matic. In such cases there may be distinctions according as there 

 is : no definite arrangement of plates or prisms, which stand in 

 all positions ; or a regular arrangement in more or less parallel 

 directions {fluidal or parallel fabric"), or in more or less radiatng 

 directions ( radiate fabric ) . 



B. Interposition (inclusion). — The arrangements of crystals 

 referred mainly to inclusion of one by another are of two princi- 

 pal kinds : 



a) Graphic fabric. — One in which two minerals mutually 

 inclose one another, by interpenetration. This is shown by the 

 parallel orientation of several parts of each mineral. The famil- 

 iar example is the graphic intergrowth of quartz and feldspar. 



b) Poikilitic fabric. — The second kind of interposition fabric 

 is that in which one mineral acts as a matrix for one or more 

 kinds of other minerals which do not possess parallel orienta- 

 tion. This is exhibited by various rocks, in some of which horn- 

 blende crystals form the matrix, in others orthoclase, in others 

 quartz. 



Ophitic fabric is a special case of poikilitic, in which plagio- 

 clases are inclosed in augite crystals, the feldspars being rela- 

 tively large when compared with the areas of augite. 



C. Porphyritic fabric is one characterized by the presence of 

 crystals surrounded by a matrix noticeably distinct from them. 

 These crystals are known as phenocrysts. The matrix or 

 groundmass may be crystalline or glassy. The phenocrysts 



