( 131 ' ) 
AiiT. l^TS^.^^Accoimt ~<^ Comptoniie, WNew Mhwral from 
Vesuvius'. By I>avid Brewster, LL. D., F. R. S. Lond. 
and Seci B. S. Edin^ &c. &c. 
-Among a number of minerals which Mr Heuland was so kind 
as to send me in 1818, for the purpose of optical examination, 
thefe was one from Vesuvius, which he loumedi Apophyllite ? 
New, and which I find has been considered as an apophyllite by 
other mineralogists. As I had previously investigated the op- 
tical structure of the different Apophyllites from Iceland, Faroe, 
Uton, and Fassa, I was prepared for the examination of this 
mineral, and soon convinced myself that it was a new species al- 
lied to the Mesotypes. 
Having subsequently learned that this substance was obtain- 
ed in Italy a few days after its discovery , and was first brought 
to England by Earl Compton, I gave it the name of Comptonite, 
as a mark of respect to a nobleman whose mineralogical know- 
ledge, and ardent zeal for the advancement of the science, have 
placed him in the chair of the Geological Society of London 
Crystallographic Structure.^^Comptomie is found in small 
transparent or semi-transparent crystals, lining the cavities of an 
amygdaloidal rock from Vesuvius "I-. The crystals which I have 
examined, have the form of right prisms, nearly rectangular, 
with plane summits ; or the same figure truncated on the lateral 
edges, so as to compose an eight-sided prism. This last form is 
the most common ; but though some of the crystals are very per- 
fect and beautiful, yet there is such an irregularity on the faces of 
the prism, that it is impossible to obtain very precise measurements 
of the angles. The following are the angles which I obtained, 
(see Plate III. Fig. 4.) 
I S 
• This mineral was first found by Salvator Madonna, the principal guide to 
Mount Vesuvius, in the month of September 1817, Mr Allan suggested to die 
the propriety of the name which I have adopted. 
•f* In some of Earl Compton’s specimens, it is accompanied with AcicularAr- 
ragonite. 
