The most common phenocryst silicate phases are olivine, plagioclase and augite
, typically, although not always, appearing in that order (Fig.
Opaque minerals occur as inclusions within plagioclase and augite
, and as discrete tiny grains in the groundmass.
Calculations used the augite
and plagioclase analyses portrayed in Fig.
[FIGURE 7 OMITTED] Table 1 Mineral assemblages for Hurricane Mountain samples, and two samples from Boil Mountain Mafic Felsic 114 158 163 116 147 Augite
X X X Serpentine Actinolite X X K-feldspar X X Plagioclase X X X Chlorite X X X X X Epidote X X X X X Pyrite Quartz X X Biotite X X X Muscovite X X Titanite Il-Spinel group X Felsic Ultramafic Boil Mtn.
In tephrite and trachybasalt the phenocryst of plagioclase, augite
, olivine, pargasite and phlogopite are embedded in the groundmass of plagioclase, Ti-augite, pargasite, phlogopite, apatite, opaque minerals (ilmenite) and devitrified glass (Sawada et al., 1992).
In 1819 MacNeven described "white augite
[diopside] in nearly rectangular prisms" from the Kingsbridge quarry and noted that "[this] was, for a long time, the only locality for this mineral in the United States, but Mr.
Biotite Calcite Chlorite Chromite Fluorite Galena Hematite Ilmenite Leucoxene Limonite Magnetite Muscovite Olivine Orthopyroxene Pervoskite Phlogopite Pyrite Quartz Serpentine Sphalerite Titanite
The rock they found is an ophitic augite
diabase with clay-lined fractures containing well-crystallized "dipyramidal" blue quartz.
Other species include dark green prisms of sodic augite
to 3 cm, and 3-4 mm sprays of mordenite.
Simple black prismatic crystals of titaniferous diopsidic augite
(Joplin, 1964) reaching 5 mm in length are occasionally observed in the miarolitic cavities associated with the pegmatite schlieren.
phenocrysts more strongly Augite
phenocrysts generally pleochroic having purplish-brown, pale-brown and zoning is not as Tirich rims.