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Formula: Y5(SiO4,BO4)3(OH,O,F)
Nesosilicate (insular SiO4 groups), britholite group
Specific gravity: 3.05 to 3.40
Hardness: 3½ to 6½
Colour: Dark green-black, red-brown, nearly black
Solubility: Gelatinises in hydrochloric acid
RADIOACTIVE
Environments
Tritomite-(Y) occurs in granite
pegmatites and
pegmatite veins cutting
pyroxenite
(HOM).
Localities
At the type locality is an unnamed prospect pit, Cardiff Township, Haliburton County, Ontario, Canada,
tritomite-(Y) occurs as masses in a narrow pegmatite
stringer in a vuggy pyroxenite, associated with
calcite, apatite,
diopside, fluorite and
scapolite. Cracks in the tritomite-(Y) contain a fine-grained white carbonate high
in yttrium (AM 46.1204). Other associated minerals include
zircon, quartz,
albite variety oligoclase, microcline,
magnetite, titanite variety keilhauite,
fergusonite, biotite,
apatite, clinopyroxenes and
amphiboles
(Mindat, HOM).
At the Faraday Mine, Faraday Township, Hastings County, Ontario, Canada, tritomite-(Y) is associated with
albite, calcite,
arfvedsonite, pyrite,
quartz and tourmaline
(HOM).
Near Cranberry Lake, Sussex county, New Jersey, USA, tritomite-(Y) occurs in a
granite pegmatite
composed of microcline,
quartz, albite variety oligoclase,
magnetite, black zircon,
clinopyroxene, amphibole,
fergusonite, titanite variety
keilhauite,
apatite, tourmaline,
biotite, fluorite and
galena. It is intimately associated with
magnetite,
black zircon, apatite, and
fergusonite, although it contains no
niobium
or tantalum and
only traces of zirconium or phosphorus. Zircon found in Precambrian rocks is
usually brown, red, or hyacinth in colour;
it is rarely black. It would appear that this part of the New Jersey highlands is an
yttrium-rich
as well as a magnetite-rich province, thus, tritomite-(Y), rather than
tritomite-(Ce), was formed in the
pegmatites of this
area. The Langesundsfjord pegmatites, which contain
tritomite-(Ce), are
enriched in rare earths predominantly of the cerium group
(AM 47.9-25).
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