176 EDSON S. BASTIN 



are perfectly fresh. Within the larger plates inclusions of titanite, 

 often forming a border about ilmenite or titaniferous magnetite, 

 are abundant. Some zircon and numerous apatite prisms are also 

 inclosed. 



The hornblende individuals seldom exceed ^ ^"^ in diameter, 

 but are usually grouped in aggregates which may be 2 to 3 "^^ 

 across. The color is light green, and the pleochroism is not marked. 

 The aggregates inclose some biotite, some titanite, and abundant 

 prisms of apatite. 



Titanite occurs abundantly in small grains, but larger aggre- 

 gates are usually associated with a mineral showing the optical 

 properties of magnetite. This mineral is probably ilmenite or 

 titaniferous magnetite. If forms a core surrounded by rather an 

 even border of titanite, or else occurs in small irregular grains scat- 

 tered through the central portion of the titanite aggregate. Some 

 of these titanite and titaniferous magnetite masses are over 1 1 ™™ 

 in diameter. This association suggests that the titanite is a decompo- 

 sition product from the titaniferous magnetite. This decomposition 

 is somewhat remarkable in view of the exceedingly fresh state of 

 the hornblende and the biotite; but it seems improbable that the 

 titanite and titaniferous magnetite are in parallel growth, or that the 

 hornblende and biotite owe their fresh appearance to recrystalli- 

 zation. 



Apatite is very abundant in short prisms averaging about ^ "^^ 

 in diameter. These are inclosed by all the other constituents of 

 the rock, even by the titaniferous magnetite. 



Quartz occurs, mainly about the borders of the feldspar pheno- 

 crysts, in small grains which are usually aggregated. 



Feldspar is present only rarely in the groundmass, and is then 

 usually close to the phenocrysts. It is microcline or orthoclase. 



In some of the feldspar phenocrysts we find inclosures which 

 have the same mineral composition as the groundmass. Upon care- 

 ful examination, these are seen to occur along lines of healed frac- 

 ture. When several such inclosures occur in the same phenocryst, 

 they seem to be connected by an irregular band of feldspar differing 

 slightly in appearance from the rest of the phenocryst. This differ- 

 ence may consist (i) in a lesser abundance of minute inclusions, 



