4 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.66. 



DETAILED DESCRIPTION. 



OUTLINE. 



The following detailed description may be represented by the fol- 

 lowing outline although the treatment does not strictly adhere to the 

 outline^in its entirety. 



1. Jointing and fissuring. 



2. Normal diabase. 



a.^Macroscopic features. 

 h. Texture. 

 c. Minerals. 



(1). Feldspar. 

 (2). Pyroxene. 

 (3). Accessories, 

 (a) Iron ore. 

 (6) Biotite. 



(c) Quartz and micropegmatite. 



(d) Apatite. 



3. Diabase Pegmatite. Definition. 



a. Macroscopic features. 

 &. Texture. 

 c. Minerals, 



(1) Feldspar. 



(2) Pyroxene. 



(3) Accessories. 



(a) Micropegmatite. 

 (&) Ilmenite, Iron ore. 



(c) Biotite. 



(d) Apatite. 



(e) Alteration products. 



4. Albitic pegmatites — definition. 



a. Macroscopic features. 

 h. Texture. 



c. Minerals. 



(1) Feldspar. 



(2) Micropegmatite. 



(3) Pyroxenes. 



(4) Titanite. 



(5) Apatite. 



d. Composition. 



e. Origin and comparison. 



5. Aplitic albite rocks. 



a. Occurrence, size. 



h. Macroscopic features. 



c. Microscopic features, texture. 



