Images
Formula: Cu6Y(PO4)3(OH)6.3H2O
Valence: Cu2+6Y(PO4)3(OH)6.3H2O
Hydrated phosphate, mixite group,
yttrium- and copper- bearing mineral
Crystal system: Hexagonal
Specific gravity: 3.41 measured, 3.40 calculated
Hardness: 3 to 4
Streak: White
Colour: Yellowish green
Luminescence: No fluorescence observed under UV
Solubility: Readily soluble in 1:1 hydrochloric acid, colouring the solution light greenish yellow
Common impurities: Ce,Nd,La
Environments
Localities
At Herrensegen Mine, Wildschapbach valley, Bad Rippoldsau-Schapbach, Freudenstadt, Karlsruhe Region, Baden-Württemberg,
Germany, petersite-(Y) is associated with malachite and
quartz (dubious locality)
(HOM).
The type locality:, Laurel Hill, Secaucus, Hudson County, New Jersey, USA, consists of a plug of
dolerite cutting sediments, which originally were
ferruginous (containing iron oxides) sediments, now metamorphosed into a
biotite-plagioclase
hornfels. Petersite-(Y) occurs wholly within the
hornfels located approximately 30 to 60 m from the northern contact
with the dolerite stock. The
hornfels has been extensively
brecciated in places and subjected to
secondary mineralisation.
Petersite-(Y) occurred in minute cavities between brecciated
hornfels fragments where approximately a dozen hand-sized samples were
recovered; it occurred in several assemblages.
The originally discovered material occurred on a matrix of severely altered
chalcopyrite, which was coated with an amorphous dark red mineral
similar to pitticite, but more likely near
diadochite in composition, given the geochemistry of the occurrence. This
in turn was coated with abundant malachite and
chrysocolla, coated with
hematite and a thin, desiccated layer of light bluish amorphous
opal. The final mineralisation was of
malachite, in small mammilary aggregates, coated sparingly with tiny
clusters of petersite-(Y) crystals. Although petersite-(Y) occurs in other assemblages, the best formed
and largest crystals occur within this altered sulphide assemblage. Petersite-(Y) encrusted both the
opal and the malachite.
A second assemblage consists of white albite with or without
chlorite, malachite and
anatase, the last in bright euhedral crystals. These minerals are coated with
light blue opal and, lastly, petersite-(Y). Petersite-(Y) may form
on any of these minerals but it is usually found on the light blue opal. Other
samples occur in slightly varied assemblages with cloudy albite which gives a
greyish appearance to the matrix. In these samples, the opaline coating is more
glassy and chalcedonic as compared with the desiccated appearance of the
previously described assemblages.
Petersite-(Y) appears to be a supergene mineral with
copper derived from the altered
chalcopyrite. The origin of the
rare earth elements and phosphorus is problematical. However,
allanite and apatite are known to
occur at the locality and alteration of these minerals may well have provided the
rare earths
(AM 67.1039-1042 as petersite).
Petersite-(Y) from Laurel Hill -
Image
Back to Minerals