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Formula: Ca3Si3O8(OH)2
Sorosilicate (Si2O7 groups)
Crystal System: Triclinic
Specific gravity: 2.89 measured, 2.905 calculated
Hardness: 4½ to 5
Streak: White
Colour: White, beige, colourless, yellow-brown
Luminescence: Fluoresces light orangish pink under long wave UV
Solubility: Slightly soluble in concentrated acids
Common impurities: B,Al,Fe,Mn,Mg,Sr,Ba,Na,H2O
Environments
Localities
At Staré Ransko, Krucemburk, Havlíčkův Brod District, Vysočina Region, Czech Republic, rosenhahnite is
associated with prehnite,
xonotlite
and pectolite
(HOM).
At the type locality, the Rosenhahnite occurrence, Russian River, Cloverdale area, Mendocino county, California,
USA, rosenhahnite is primarily a vein-forming mineral in dark grey boulders, one to three feet in diameter.
Narrow veinlets less than 3 cm thick of buff to white, massive rosenhahnite transect
brecciated, fine-grained metasedimentary rock. Occasionally open
spaces within the buff-coloured veinlets contain clear as well as etched, flat tabular crystals of
rosenhahnite. One specimen contains hollow opal
pseudomorphs after rosenhahnite. Some white massive veinlets
consist of a mixture of rosenhahnite, pectolite and
xonotlite; others contain rosenhahnite,
diopside, garnet and
calcite. The calcite partially
replaces rosenhahnite and diopside.
The dense, grey host-rock is composed of fine-grained diopside with
variable amounts of hydrogrossular, finely fibrous aggregates of
tremolite and minor titanite.
Specimens may also contain rosenhahnite in the matrix.
Xonotlite occurs as radial acicular aggregates intergrown with
rosenhahnite. Crystals of acicular pectolite and equidimensional
datolite are attached to crystals of rosenhahnite in cavities and
appear to be later than rosenhahnite. A 0.5 mm-thick veinlet of
datolite was found cutting veinlets of rosenhahnite in one specimen.
The bedrock in the vicinity of the rosenhahnite locality is a
sandstone which is composed essentially of
quartz, albite and
chlorite with veins of quartz and
calcite. Leonhardite coats
fractures in some outcrops. This sandstone is in tectonic contact
with altered dolerite composed of
augite, altered plagioclase,
chlorite and quartz with veins of
radiating buff prehnite and quartz.
Locally breccia zones up to one foot thick occur along the contact
between the sandstone and
dolerite. Other rocks in the vicinity include
serpentinite, chert,
hard black shale and blocks of
glaucophane schist,
all of which contain numerous veinlets, mainly of quartz and
calcite, but some rocks also contain veinlets of
pectolite, xonotlite,
datolite and apophyllite
(AM 52.336-351).
At Durham Quarry, Durham, Durham county, North Carolina, USA, rosenhahnite is associated with
prehnite, gyrolite,
okenite and apophyllite
(HOM).
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