The erionites are:
Erionite-Ca, Ca5[Si26Al10O72].30H2O
Erionite-K, K10[Si26Al10O72].30H2O
Erionite-Na, Na10[Si26Al10O72].30H2O
They are all tectosilicates (framework silicates) and members of the zeolite group.
Specific gravity: 2.09 to 2.13
Hardness: 3½ to 4
Streak: White
Colour: Colourless, white, green, grey, orange
Environments:
Volcanic igneous environments
Sedimentary environments
Basaltic cavities
Erionite is common in altered silicic tuff, especially in saline lake deposits, where
it crystallises when the pH reaches about 8.5 (moderately alkaline). In this environment trivalent iron may substitute
for aluminium in the structure
(AM54.875-886).
Hydrothermal erionite occurs in cavities in volcanic rocks. It is often intergrown with
offretite.
Epitaxial overgrowths of erionite on lévyne have been reported
(AM83.577-589).
At Pauliberg, Burgenland, Austria, erionite needles are found on primary
magnetite and hematite in
vesicular basalt.
In the basalt at Kollnitz, Carinthia, erionite is found on
celadonite associated with pyrite,
calcite and
phillipsite.
At Chase Creek, British Columbia, Canada, pure erionite without any
offretite intergrowth occurs in
vesicular basalt, rarely covered by
paulingite,
harmotome, heulandite and
clay.
At Pass Valley, British Columbia, Canada, erionite intergrown with clay and associated with
clinoptilolite occurs in vesicles in
rhyolite.
At Twig Creek, British Columbia, Canada, erionite crystals capped by offretite
line vesicles in basalt
(ZoW161-162).
Erionite covered with chabazite occurs in
basalt in the Faroe Islands, Denmark
(ZoW161-162).
Near Araules, Auvergne-Rhône-Alpes, France, offretite intergrown with small amounts
of erionite is found in basalt, associated with
phillipsite, chabazite and
calcite.
At Mont Semiol, Auvergne-Rhône-Alpes, France, erionite is found as terminations on
offretite crystals in olivine
basalt, associated with
mazzite-(Mg),
phillipsite, chabazite,
calcite and siderite.
(ZoW161-162)
At Shurdo, Georgia, erionite occurs in volcanic rock associated with heulandite,
chabazite, mordenite,
stilbite and opal
(ZoW161-162).
At Sasbach, Baden-Württemberg, Germany, offretite-erionite occurs in vesicles in
nepheline - olivine -
augite basalt, associated with
faujasite and
phillipsite.
At Teichelberg, Bavaria, Germany, offretite-erionite occurs in cavities in
basalt associated with gismondine,
phillipsite, calcite and
chabazite.
At Wiesau, Bavaria, Germany, erionite-offretite occurs in
basalt with thomsonite and
montmorillonite.
At the Zeilberg Quarry, Bavaria, Germany, erionite is found in basalt with
dachiardite, clinoptilolite,
phillipsite, natrolite,
heulandite,
thomsonite,
laumontite, scolecite,
stilbite, gmelinite,
chabazite, gismondine,
apophyllite, calcite,
gyrolite, okenite,
garronite and
tobermorite.
Near Gedern, Hessen, Germany, erionite is found in the extremities of offretite needles
in vesicular basalt, associated with
phillipsite, chabazite,
montmorillonite and, rarely,
gismondine.
At Geilhausen, Hessen, Germany, offretite covered by erionite occurs in vesicles in
olivine basalt, associated with
chabazite and phillipsite.
At Hungen, Hessen, Germany, erionite-offretite occurs with
chabazite, faujasite,
ferrierite, lévyne,
phillipsite and thomsonite.
At the Ortenberg Quarry, Hessen, Germany, erionite is found, rarely, in vesicles in a
sandstone
xenolith embedded in
olivine basalt, with
paulingite,
clinoptilolite,
nontronite, phillipsite,
calcite, dachiardite,
merlinoite, apophyllite and
chabazite
(ZoW161-162).
At Nuoro, Sardinia, Italy, erionite is found as overgrowths on lévyne
(ZoW161-162).
Erionite on lévyne crystals is found in
vesicular basalts at Chojabaru, Nagasaki Prefecture, Japan, associated with
chabazite and stilbite.
At Narushima, Nagasaki Prefecture, Japan, erionite occurs with heulandite in the
glassy margins of a rhyolite dyke.
Along the seashore of Maze, Niigata Prefecture, Japan, erionite is found associated with
chabazite
(ZoW 161-162).
At Waitakere, North Island, New Zealand, erionite is found surrounded by lévyne.
At Moeraki, South Island, New Zealand, erionite occurs in altered vesicular basalt
associated with chabazite, heulandite
and phillipsite
(ZoW161-162).
In lavas along the Nidym River, Siberia, Russia, erionite is associated with
heulandite
(ZoW161-162).
At Lake Natron, Arusha Region, Tanzania, erionite is associated with phillipsite,
mordenite, analcime and
chabazite.
In the Olduvai Gorge, Arusha Region, Tanzania, erionite is abundant in sedimentary beds associated with
phillipsite, clinoptilolite,
chabazite and analcime
(ZoW161-162).
At Giant's Causeway, County Antrim, Northern Ireland, UK, erionite occurs in basalt
associated with heulandite and
phillipsite.
Erionite is often intergrown with offretite on
lévyne at many localities in County Antrim, Northern Ireland, UK.
At the Storr, Isle of Skye, Scotland, UK, erionite occurs in vesicles in basalt
with massive garronite
(ZoW161-162).
Near Ajo, Arizona, USA, erionite occurs in vesicular basalt associated with
phillipsite, heulandite and
calcite on the primary minerals
hematite, augite,
kaolinite, enstatite,
pseudobrookite and
rancieite.
At Malpais Hill, Arizona, USA, in vesicular olivine
basalt, small vugs are lined with celadonite
and montmorillonite covered with
offretite intergrown with erionite.
At Thum Butte, Arizona, USA, erionite occurs in vesicular olivine
basalt associated with quartz,
mordenite, clinoptilolite,
phillipsite and opal.
Near Freedom, Idaho, USA, erionite occurs in vesicular basalt with
chalcedony and opal.
At Reese River, Nevada, USA, erionite occurs in lacustrine (deposited in a lake)
mudstone associated with
clinoptilolite, chabazite and
phillipsite.
Near Aneroid Lake, Oregon, USA, erionite occurs in vesicular basalt,
frequently covered with heulandite.
At the Durkee fire-opal mine, Oregon, USA, some erionite fibres are found covered by common
opal and, rarely, fire opal.
At Yaquina Head, Oregon, USA, erionite occurs in vesicular basalt associated
with clinoptilolite, mordenite,
phillipsite, pyrite and, rarely,
dachiardite and baryte
(ZoW161-162).
Along the Beaver Divide, Wyoming, USA, erionite and clinoptilolite occur
in altered tuff.
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