PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 455 



Mesolite. ] 



Owing to the abundance of this green substance, which is crypto-crystalline and has 

 replaced some earlier idiomorphic mineral, it is probable that aiigite of an earlier 

 generation has shared in its formation. The later augites are well preserved. They 

 embrace many microlitic feldspars and occasionally some of the thalite areas. It is 

 to be noted also that, while most of these green areas have shapes showing they are 

 changed from an early generation of some mineral, either olivines or first augites, 

 there are a few that are ophitic in their relation to some of the feldspars. These 

 probably resulted from an alteration of small portions of the magmatic residue. 

 This is evident from the fact that the ophitic augites are all quite fresh. Heulandite 

 appears in clear grains in the slide. 



One section. 



Age. Manitou. N. H. w. 



No. 625A. MESOLITE. 



t 



Picked from the rock at Eclipse beach. 

 Ref. Annual Report, x, page 60. 



Mr//. Strongly but finely radiated, pinkish white, filling large cavities in the 

 trap (No. 625). The fibres are strong, straight and rigid, but fine, differing from 

 those of thomsonite and scolescite, which are coarser and have a glassy reflection 

 and greater transparency.. 



Some of the masses of this mineral are three or four or even ten inches across; 

 but in the case of large masses the mineral lies rather in sheets with radiating points 

 on the upper and lower contact surfaces. Some large masses two inches across have 

 also two or three points of radiation. When polished on the beach the pieces that 

 result from the disintegration of the larger masses are pyramido-triangular, but there 

 are also many round and oval which have not been broken on separation from the 

 rock. These show the circular radiating eyelets of different colors on the outer sur- 

 faces when polished on the beach. The colors are pink, red, white and green at 

 least the same green mineral is found here, always smaller than the others, as is 

 found at Terrace point. This green mineral ( "lintonite " ) often surrounds the pink 

 and white radiating masses. It is itself not evidently radiated, the radiations of the 

 mesolite penetrating it. Sometimes little nests and rosettes of lintonite grow in the 

 mesolite, prevailingly about the peripheries of the mesolite masses. 



Mlc. In very thin section this mineral is nearly unresponsive to all changes 

 of the stage, whether in parallel or convergent light. All the sections made from 

 this number seem to contain two minerals very intimately intermixed. The sub- 

 opaque white fibres are interspersed with parallel translucent ones, but between 

 crossed nicols these translucent fibres are constantly dark and are generally much 

 coarser than the sub-opaque ones. Indeed these transparent larger fibres show 



