Images
Formula: (Ca,REE)4Y2Al☐2(B4Si4O22)(OH)2
Nesosilicate (insular SiO4 groups), borosilicate,
hellandite group, yttrium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 2.95 to 3.63 measured, 3.5 calculated
Hardness: 4½ to 6½
Colour: Nut-brown, brownish red, black, grey, green, yellow, cream, pinkish
Environments
Hellandite-(Y) occurs in granitic
pegmatites associated with
xenotime, wakefieldite,
thorogummite, quartz,
kainosite-(Y), fergusonite and
chlorite group minerals
(Mindat).
Localities
Hellandite was redefined as hellandite-(Y) by the IMA in 2000, so in the references cited below "hellandite" is assumed to
refer to hellandite-(Y).
There are 5 co-type localities:
Mattagami Lake mine, Matagami, Nord-du-Québec, Québec, Canada
Evans-Lou Mine, Lac Saint-Pierre, Val-des-Monts, Les Collines-de-l'Outaouais RCM, Outaouais, Québec, Canada
Quyang pegmatite, Quyang County, Baoding, Hebei, China
Tawara, Hirukawa, Nakatsugawa City, Gifu Prefecture, Japan
Lindvikskollen Quarry, Lindvikskollen-Kalstadgangen pegmatite, Kragerø, Vestfold og Telemark, Norway
At the Evans-Lou mine, Lac Saint-Pierre, Val-des-Monts, Les Collines-de-l'Outaouais RCM, Outaouais, Quebec, Canada, the
abandonned quarry exposes a pegmatite dyke that contains
fergusonite, kainosite-(Y),
tengerite-(Y), xenotime,
wakefieldite and hellandite. The
pegmatite cuts metamorphic rocks and is zoned with a
quartz core, giant
perthite-quartz zone,
perthite-plagioclase-quartz
zone and graphic granite (on the periphery). Rare earth minerals are mainly
concentrated in the giant
perthite-quartz zone.
Passing from the
perthite-plagioclase-quartz zone into
the giant perthite-quartz zone we
progressively encounter the following assemblages:
apatite - fergusonite -
titanite, titanite -
fergusonite - allanite and
titanite - allanite -
spessartine. Near the quartz core
there is a strong enrichment in boron, and hellandite appears along with
fergusonite, some spessartine
and rare allanite. All these phases are associated with
quartz-rich portions of the
pegmatite. Euxenite
and tourmaline are also seen but not in association with hellandite.
Hellandite found on the dump commonly occurred in quartz, was spotted
with chlorite, veined by red
kainosite and stained white by
tengerite-(Y). Less common alteration products were
hematite, calcite,
thorogummite, synchysite-(Y) and,
perhaps, wakefieldite. In situ hellandite has been found abundantly
in greyish quartz-rich portions of the giant
perthite-quartz zone close to the
barren white quartz core. Commonly hellandite,
quartz and microcline are
brecciated and cemented with a new generation of
quartz. Fergusonite is a common
associate of hellandite. Other primary minerals sometimes
seen near hellandite include yttrium-bearing
spessartine,
allanite, uraninite,
specularite, muscovite,
pyrrhotite and chalcopyrite
(CM 11.760-776).
At Predazzo, Trento Province, Trentino-Alto Adige, Italy, hellandite occurs in
granite associated with a niobium
oxide, allanite and various
yttrium-bearing minerals
(CM 11.760-776).
The Heftetjern pegmatite, Tørdal, Drangedal, Vestfold og Telemark, Norway, is a
scandium-rich
cleavelandite-amazonite
granitic pegmatite.
A striking feature of the Heftetjern pegmatite is the high level
of scandium. Beryllium,
yttrium, tin and
tantalum are also characteristic elements. the Tørdal
pegmatites are of mixed LCT
(lithium, cesium,
tantalum) and NYF (niobium,
yttrium, fluorine) types.
Here, zinnwaldite and
cassiterite are the most common
lithium and tin minerals, respectively.
The Heftetjern pegmatite is famous for its unique assemblage of
scandium minerals such as
kristiansenite, oftedalite
and heftetjernite, as well as
bazzite, scandiobabingtonite,
cascandite and thortveitite
(CM 53.345-356).
A manganese-bearing hellandite-(Y) has been found as tiny pinkish
yellow granular crystals in the pegmatite
(Mindat).
At Lindvikskollen Quarry, Lindvikskollen-Kalstadgangen pegmatite, Kragerø, Vestfold og Telemark, Norway, hellandite
is associated with a niobium oxide,
allanite and various yttrium-bearing
minerals
(CM 11.760-776).
At Fabova hoľa, Pohronská Polhora, Brezno District, Banská Bystrica Region, Slovakia, two contrasting reaction coronae
were developed around rare earth element accessory phosphates in
metagranitic rocks.
Monazite-(Ce) breakdown resulted in impressive, though common,
fluorapatite ± thorium-silicate
+ allanite-(Ce) +
clinozoisite coronae. The alteration of
xenotime-(Y) produced a novel type of
secondary coronae consisting of a massive
fluorapatite mantle zone and tiny satellite crystals of
hellandite-(Y) and hingganite-(Y). The localised occurrence of
yttrium–boron–beryllium
silicates, which are associated closely with other secondary
minerals, suggests the involvement of boron and
beryllium during the metasomatic alteration of
xenotime-(Y).
The granitic rocks underwent burial metamorphism under
greenschist to lower
amphibolite facies conditions. Subsequently, uplift and
exhumation was accompanied by retrograde metamorphism; the activity of external fluids caused the formation of
secondary coronae minerals around
monazite-(Ce) and
xenotime-(Y)
(MM 86.4.586–605).
Back to Minerals