Boracic Acid in Minerals. 
127 
though found in such different parts of the world, it would seem 
to be an essential ingredient of tourmaline, as was rendered pro- 
bable by the analyses of the chemists already referred to. The 
varieties from Aberdeenshire and Penig are specimens of com- 
mon schorl, which occur in granite. The feldspar, in contact 
with the schorl, was carefully examined, but did not give the least 
indication of boracic acid. 
As the process just described is of easy and rapid execution, 
and requires but a minute fragment of each specimen, I have 
not failed to examine a considerable number of minerals by this 
mode ; and Mr Allan, with his usual liberality, has kindly sup- 
plied me from his cabinet with whatever was necessary for the 
purpose. The following list contains a few of the minerals so 
examined, in which no boracic acid could be discovered : 
Pumice and Obsidian, from Lipari. 
Pitchstone, from Arran and Meissen. 
Greenstone, of Salisbury-Craig. 
Basalt, of Arthur’s Seat. 
Common Hornblende, from Arendal. 
Crystallised Hornblende, from Bohemia. 
Augite, from Bohemia, 
Common Garnet, from Greenland. 
Bohemian Pyrope. 
Pistacite, from Norway. 
Feldspar. 
Leucite. 
Idocrase. 
Zoizite. 
Lava, origin unknown. 
Axinite, on the contrary, though no boracic acid has hitherto 
been discovered in it, does certainly contain that substance ; for, 
when treated by the flux, it yields precisely the same appearance 
as tourmaline. I first observed it in a specimen of my own, the 
locality of which is uncertain, but have since found it in crystal- 
lised axinite from Dauphiny and Cornwall, so that it is probably 
an essential ingredient of that mineral. The kind of rock from 
Cornwall, called Massive Axinite, does not contain boracic acid. 
I possess a specimen of colophonite from Norway, supposed 
to be from Arendal, which likewise contains boracic acid. It 
appears, however, to be only an accidental ingredient ; at least, 
two other varieties from Arendal, and a third from America, do 
not contain it. 
It has of course been proved, that the green flame produced 
by the flux in tourmaline, axinite, and one variety of colophonite, 
was really occasioned by boracic acid. A specimen of Brazilian 
tourmaline, for example, was ignited with three times its weight 
of carbonate of soda ; water was added, and the alkaline solution, 
after being neutralised by a slight excess of sulphuric acid, was 
