Mr. Brooke on some undescribed Minerals, 275 





amining them, but it is now several months since I ascertained 

 from the measurement of their angles that they differed from the 

 crystals of every other known mineral. They are so very minute, 

 that the whole quantity I possess would weigh only a few grains. 

 A part of one of the specimens, however, enabled Dr. Wollaston 

 to ascertain that the mineral was a Phosphate of Alumina and Iron. 



The attention which Mr. Children has shewn to mineralogical 

 chemistry, is one, among many other inducements to name this 

 mineral Childrenite. 



The form of the crystals is represented by the accompanying 

 figure, except in this particular, that the planes marked b, in the 

 figure, generally consist of a number of very narrow planes with 

 parallel edges, but whose inclinations upon e, I have not been 

 able to measure. 



I have not succeeded in cleaving the crystals, but we may as- 

 sume aright rhombic prism as their primary form; and if we 

 suppose the planes e to be produced by decrements upon itb ter- 

 minal edges, the lines between e e, and e" e", would obviously lie 

 on the lateral primary planes, and the inclination of these planes 

 would then be 92° 48'. 



If the planes e result from a decrement, by one row of mole- 

 cules, the terminal edge would be to a lateral edge, nearly as 

 1 3 to 28, and the planes a might then be represented by the 

 symbol .. 



The crystals slightly scratch glass. Their colour is wine yel- 

 low. And in the only specimens I have seen they occur on the 

 surface of crystallized quartz, and might be mistaken by a casual 

 observer for sulphate of barytes. 



Somervillite. 



The next mineral I shall have to describe came to me with some 

 T 2 



