216 ES. Dana—Garnets from the Trap Rocks of New Haven. 
Garnets from East Rock. 
nar, and the garnets occur on the vertical surfaces of the 
front of the Rock, failed to reveal any other locality. 
The associated minerals are: Magnetite, apatite, pyroxene 
now altered to chlorite, calcite, and also in traces chalcopyrite 
and sphalerite. 
The garnets themselves are uniformly crystallized in rhombic 
dodecahedrons, with the edges truncated by the planes 2-2. 
; : 
crystalline crusts which have been mentioned. It was selected 
with care to ensure freedom from the rock, and still more from 
the apatite crystals, which, as remarked below, were intimately 
associated with the garnet. The specific gravity was 3°740. 
e mean of two analyses gave: 
BOG: o.oo Be 
Tron sesquioxide (with AlO, trace). .-..----- 29°15 
ron protoxide 23). iui oo. Me Oe emer 2°49 
Manganese protoxide_... .. 0.0 2l en esse 0°36 
NO So te Oe es ee 32°80 
Maonesig posit, scsi oe seus fa 3s sesh Ge 0°24 
APUIRION [ois ad ee, 26s ee ie ween oe 
100°48 
