302 DESCRIPTIONS OF MINERALS. 
to a white translucent glass. Gives water in a closed glass 
tube. Partially decomposed by hydrochloric acid, and if 
sulphuric acid be added to the solution, 
a heavy white precipitate of barium sul- 
phate is formed. Some varieties phos- 
phoresce when heated. 
Diff. Its twin crystals, when distinct, 
cannot be mistaken for any other species 
except phillipsite. Much more fusible 
than glassy feldspar or scapolite; does 
not gelatinize in acids like thomsonite. 
\ Obs. Occurs in amygdaloidal trap, 
and in trachyte and phonolyte, also in 
gneiss, and metalliferous veins. Fine 
erystallizations are found at Strontian in Scotland, and 
in Dumbartonshire; Andreasberg in the Hartz; Kongs- 
berg in Norway. Has been found in seams in the gneiss 
of the upper part of New York Island. 
The name harmotome is from the Greek harmos, a joint, 
and temno, to cleave. 
Phillipsite. Near harmotome in its cruciform crystals and 
other characters ; but differing in containing lime in place 
of baryta. It differs also in gelatinizing with acids and in 
fusing with some intumescence. It also occurs in sheaf-lhke 
aggregations and in radiated crystallizations. From the 
Giant’s Causeway, Capo di Bove, Vesuvius, Sicily, Iceland. 
Epistilbite. A hydrous silicate of alumina and lime. Occurs in 
thin rhombic prisms, of a white color, with a perfect pearly cleavage 
like stilbite. H.=4-4:5. G.=2°25. Before the blowpipe froths and 
forms a vesicular enamel. Does not gelatinize. From Iceland and 
Hindostan, and sparingly at Bergen Hill, N. J. 
Bravaisite. Supposed to be a zeolite ; it has potassium, magnesium 
and iron as the protoxide bases. 
Stilbite. 
In pyramidally terminated rectangular prisms usually 
flattened parallel to the face 7-%. which is the 
direction of cleavage and is very pearly in lustre. 
JA1=119° 16’, and 114°. Also in sheaf-like ag- 
gregations, and thin lamellar and columnar ; also 
in pearly radiated crystallizations. 
Color white ; sometimes yellow, brown or red. 
Subtransparent to translucent. H.=35-4. G.= 
2°1-2°15. 


