Granites of Cecil County, in North-eastern Maryland. 85 



the form of small needles in biotite, quartz, and occasionally 

 in feldspar. The larger masses, as we have seen, are very 

 irregular both in form and arrangement. These smaller par- 

 ticles, however, have a definite form and usually a symmet- 

 rical arrangement. These needles are especially character- 

 istic of the biotite in very man} 7 sections of the Rowlandville 

 granite. Basal sections of the mica are most favorable for 

 their study where the needles cross each other, forming a 

 network whose angles are 60 and 120 degrees, so that they 

 resemble very strongly the well-known sagenite network of 

 rutile needles (see Fig. 3, A and B). In prismatic sections 



Fig. Kpidote needles in biotite from Rowlandville granite. 



of the biotite, they are seen along the line of the basal cleav- 

 age, and also in directions which make varying angles with 

 these, as shown in Fig. 3 C. These needles, in some cases, 

 extend unbroken from the biotite into the neighboring feld- 

 spar, preserving the same sixty-degree angles. 



In the quartz, small needles also occur, which traverse this 

 mineral in different directions. At the boundary between 

 two contiguous grains of the quartz mosaic, these needles are 

 broken. Even within a single quartz grain they are also gen- 

 erally broken and pulled apart (see Fig. 1). 



In w T hat has preceded, these needles have been described as 

 epidote, without any reference as to proof of their mineral 

 nature. At first glance they are suggestive of the sagentic 

 arrangement so common in needles of rutile. Their shape 

 and high refractive index also seem to indicate that they 

 belong to this species. Closer study, however, with high 

 magnifying powers, lead to the conclusion that these needles 

 are really epidote, like the irregular grains with which they 



