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Formula: (K,Na)5(Si31Al5)O72.18H2O
Tectosilicate (framework silicate), ferrierite subgroup,
zeolite group
Crystal System: Orthorhombic
Specific gravity: 2.06 to 2.23
Hardness: 3 to 3½
Streak: White
Colour: Colorless, white, pink, orange and red
Environments
Volcanic igneous environments
Metamorphic environments
Ferrierite is a high-silica zeolite commonly found in a silica-rich
environment. The presence of ferrierite in sedimentary (diagenetic) deposits indicates it can crystallise at
low temperatures.
Mineral association is an important aid to the recognition of ferrierite. It is commonly found with the
high-silica minerals heulandite,
dachiardite,
mordenite,
quartz and chalcedony. It is
not found with the low-silica zeolites,
levyne, cowlesite,
thomsonite, mesolite,
natrolite, scolecite,
gismondine and
garronite
(ZW).
Localities
At the Itomuka mine, Tokoro District, Okhotsk Subprefecture, Hokkaidō Prefecture, Japan, K-Na-rich ferrierite
(ie ferrierite-K) forms spherical aggregates, 2 mm to 5 mm across, of terminated, radiating blades associated
with an abundance of heulandite along with
calcite, baryte and
pyrite, in openings in an altered
andesite-tuff near
native mercury and cinnabar ore
veins
(ZW).
The type locality is the Santa Monica Mountains, California, USA.
At an Unnamed Zeolite deposit, Lovelock, Antelope Mining District, Pershing County, Nevada, USA, K-rich
ferrierite (ie ferrierite-K) was formed from altered glassy volcanic ash that fel! into saline lakes; it
occurs as very small, 0.075 mm, thin, bladed crystals in radiating groups in nearly pure sedimentary beds. The
ferrierite occurs in zoned lake deposits where the centre of the former lake (now pure ferrierite)
becomes mixed ferrierite plus mordenite →
mordenite → silica-rich
heulandite as the edge of the lake is approached. The beds
are vertically zoned from top to bottom in the order: mordenite →
mordenite plus ferrierite → pure ferrierite
(ZW).
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