Pirsson and Washington — Geology of New Hampshire. 441 



and yellow, in shreds or anhedral grains, 0*1 to 0*05 mm . Allan- , 

 ite rather rare, strongly pleochroic, clear dark brown and orange 

 yellow, zonally built ; well crystallized ; about 0*l mm ; com- 

 monly attached to iron ore or biotite. Zircon rare, colorless, 

 equidimensional subhedral grains, about 0'2-0-r iim . Iron ore 

 uncommon ; anhedral ; about 0'l mm . Traces of chlorite and 

 kaolin. Fabric porphyritic, but not markedly so, the pheno- 

 crysts being rare ; remaining grains somewhat grading in size 

 but tending to be equidimensional and interlocked. 



Mode. — The chemical analysis and the calculation of the 

 norm show that there cannot be over 4 per cent of iron ores, 

 biotite, hornblende, allanite, zircon, etc., present, the remain- 

 der being feldspars and quartz in the proportions indicated in 

 the norm. The mode is therefore normative. 



Chemical Composition. — This is shown in ~No. 1 of the table. 



For the sake of comparison a number of analyses of liparose 

 from other localities have been added and it is of interest to 

 observe how these almost identical magmas under varying 

 physical conditions have assumed different textures, so that 

 under systems of classification where texture plays an impor- 

 tant part they have been given quite different names and are 

 widely separated in the system. They are all magmas of alka- 

 lic nature, as will be shown later. 



Norm and Classification. — By using the molecular ratios 

 given in No. YI of the above table we may calculate the 

 norm to be as follows : 



Quartz 31-02 1 



Orthoclase.. 32 80 | _ , n . ■ Sal 97'2 oA 



. ... V Sal = 97-21 = = =29,1, Persalane 



Albite 31-44 ( Fern 3*3 ' ' 



Anorthite ._ 1*95 F 66-19 



j yr- = =2-1, 4, Britannare 



Q 31-02 ' ' 



Diopside... 0-46^ K o 0' + l\ T a o 0' n 9 



Hypersthene 1-46 | " CaQ / ' = -^-= 17, 1, Liparase 



Magnetite ._ 1-39 Y Fem= 3*31 



Water, etc.. 0-28 j KO' 59 



J XT ~, = — = 0*98, 3, Liparose 



Total 100-80 2 



From the consideration of the analysis and the above norm 

 and by the study of the section it is easily seen that the iron 

 ore, allanite and biotite, are present in negligible amounts and 

 that, as previously stated, the rock has a normative mode. It 

 is therefore normative granophyro-liparose, but if the slightly 

 porphyritic nature which is in no wise characteristic be 

 neglected and the small amount of biotite be taken into con- 



