380 



Review of Dana's Mineralogy. 



" Composition, — 

 Silica, 

 Alumina, 

 Protoxyd of Iron, 

 Lime, 

 Magnesia, 

 Potash, 

 Water, - 



56-831 

 12-345 

 8035 

 8-419 

 3-960 

 2-388 

 8-905 



100-883 



" 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 coaled 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 ; allowing for this, and taking the 

 iron as peroxyd, the formula will be 



(Ca,Mg,K)Si + (Al,Fe)Si 3 +3SI, 

 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+2A1 Si 2 -f 9H. 



Under Datholite we have the accom- 

 panying figure of a rare and interesting 

 form of this mineral from the new local- 

 ity of Roaring Brook, Cheshire, Conn, 

 (p. 342.) 



Epidote. — Haddam, Conn., furnishes 

 crystals of this species having the form 



