HYDROUS SILICATES — MARGAROPHYLLITE SECTION. 307 



Greece, Moravia, Spain, etc. ; also in fibrous seams at a sil- 

 ver mine in Utah. 



Aphrodite. Similar to the preceding. Mg0 3 Si + fH. From Swe- 

 den. Cimolite, a clay from the Island of Argentiera, Kimole of the 

 Greeks. Smectite, a kind of " Fuller's Earth," a name given to unc- 

 tuous clays used in fulling cloth. Montmorillonite, Stolpenite, and 

 Steargillite, are related clay-like minerals. 



Glauconite. — Green Earth. 



In dark olive-green to yellowish-green grains, or granular 

 masses, with dull lustre. II. =2. G. = 2*2-2'4. 



Composition. Essentially a silicate of iron and potassium. 

 Formula RR Oi 2 Si 4 , in which R is mainly Fe and K 2 with 

 sometimes Mg ; and R is Al, but sometimes largely Fe. Analy- 

 ses give mostly 50-58 per cent, silica, 20-24 iron protoxide, 

 4-12 of potash and 8-12 of water. B.B. fuses easily to a 

 magnetic glass. Yields water in a closed tube. 



Obs. In a more or less pure state . it forms thick beds in 

 the Cretaceous formation, and also in the Lower Tertiary 

 of Xew Jersey ; also occurs in other older rock formations 

 down to the Lower Silurian. Found also, first by Pour- 

 tales, in the pores of corals and cavities of Rhizopod shells 

 over the existing sea-bottom, showing it to be a marine 

 product, and one now in progress of formation. The grains 

 of the Cretaceous, Tertiary, and Lower Silurian beds have 

 been shown by Ehrenberg to be the casts of the interior of 

 shells of Rhizopods. The silica lias been supposed to come 

 from the siliceous secretions of a minute sponge growing in 

 the cavities that afterwards became occupied by the glau- 

 conite. 



Celadonite. A green earth with 53 per cent, of silica, from amygda- 

 loid, near Verona. Probably an impure chlorite. 



Chloropal. A massive greenish-yellow to pistachio-green compact 

 mineral, somewhat opal-like in appearance, consisting chiefly of silica, 

 iron sesquioxide, and water. Montronite, Pinguite, Ungliwarite and 

 Gramerdte are varieties of it. 



Stilpnornelane. Foliated and also fibrous, or as a velvety coating. 

 Black to brownish and yellowish bronze in color and lustre. G.= 

 3-o*4. Chiefly silica and iron oxides, with 8 to 9 per cent, of water. 

 Chalcodite of the Sterling Iron Mine, Antwerp, Jefferson County, 

 N. Y., is here included. 



Serpentine. 



Usually massive and compact in texture, of a dark oil- 

 green, olive-green, or blackish-green color ; also pale yel- 



