380 Review of Dana’s Mineralogy. 
‘* Composition, — 
—_— - . - . - - - . a | 
- - - = - - * f 
aes of ne . . : - - - 8-035 | 
ime, - - - : - - - 8-419 | 
Magnesia, oe - : - : - 3:960 
Potash, - - - - - - - 2'388 
Water, - - - . - - - - 8-905 , 
100°883 m 
« Obs.—Haydenite was first described and named by Cleaveland. It 
has since been considered chabazite, and was lately restored to its place 
as a species by Levy. It occurs coating hornblendic gneiss in fissures 
at Jones’s Falls, a mile and a half from Baltimore. The crystals seldom 
exceed a line in length, and are nearly rhombs in shape. They are 
usually coated with a brownish-green hydrate of iron, which is easily 
separated, and leaves the surface smooth and bright. Occasionally crys- 
tals are met with, consisting wholly of this hydrate of iron. The Hay- 
denite is associated with Heulandite in minute crystals.” (pp. 342, 526.) 
' This species seems to deserve a distinct consideration, notwith- | 
standing its resemblance in some respects to chabazite. 
The iron was estimated as protoxyd from the excess found in | 
the analysis, (103-355.) But there is reason to believe that the | 
lime might have been in excess ; med tae for this, and taking the 
iron’ as peroryd, the formula will 
(Ca, Mg, K veecene Fe) Si? 3H, 
which is the formula given for some chabazites, (from Parsbo- 
rough, see Dana’s Mineralogy, p. 559,) excepting half the propor 
tion of water. The analysis as it stands leads to the less proba- 
ble formula— 
6(Ca, Mg, K, Fe) Si+2Al Si? +9. 
Fig. 12. 
Under Datholite we have the accom- 
panying figure of arare and interesting 
form of this mineral from the new local- 
ity of Roaring Brook, Cheshire, Conn. 
(p. 342.) 
Epwore.—Haddam, Conn., furnishes 
— of this species acing the form 
