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Formula: Sr2TiO(Si2O7)
Sorosilicate (Si2O7 groups), strontium- and
titanium- bearing mineral
Crystal system: Tetragonal
Specific gravity: 3.950 calculated
Hardness: 3 to 4
Streak: White
Colour: Colourless
Environments
Volcanic igneous environments
Metamorphic environments
Alfredcasparite is a new mineral, approved in 2023 and to date (May 2025) reported only from the type
locality.
Localities
The type locality is Xenolith CS-034 (an alfredcasparite-bearing xenolith), Caspar quarry, Ettringen,
Vordereifel, Mayen-Koblenz, Rhineland-Palatinate, Germany. The Caspar quarry is an open quarry and part of the
Bellerberg volcano. The Bellerberg volcano is characterised by the presence of various thermally transformed
xenoliths within
leucite-tephrite lava, which
differ due to the high-temperature metamorphism conditions and variable protolith composition. This leads to the
formation of miscellaneous mineral assemblages, usually in the contact zones between xenolith and surrounding magma.
The xenolith specimen containing alfredcasparite was about 30 × 20 × 20 cm3 in size.
Alfredcasparite rarely forms flattened crystals up to 30 μm across; more common are irregular grains which do
not exceed 15 μm in size.
The type material with alfredcasparite is highly diverse, especially in the case of rock-forming and accessory
minerals.
The main components of the analysed xenolith include sanidine,
quartz, various pyroxenes like
diopside-hedenbergite,
aegirine, and less often
clinoenstatite,
wollastonite, titanite,
gehlenite, fluorapatite and
cuspidine. Additionally, iron-bearing
wollastonite and highly iron-rich
sanidine were also identified. Subordinately,
wadalite, strontium-rich
fluorapatite and minerals of the
andradite-grossular and
åkermanite-alumoåkermanite
series were detected as well. The accessory minerals are represented by
oxyspinel group minerals
(spinel, magnetite,
magnesioferrite),
perovskite, chalcopyrite,
zirconium-bearing minerals such as
zircon, baddeleyite, and phases
stoichiometrically (having its component elements present in the exact proportions indicated by its formula)
corresponding to calzirtite, and
baghdadite. In addition to alfredcasparite, two other
strontium-bearing accessory phases were identified: a potentially new
mineral with a chemical composition close to (Sr2Na)Ti(Si2Fe)Si2O14, and
wesselsite. Moreover, the cavities and cracks of the xenolith are filled
by secondary, low-temperature minerals such as
fluorapophyllite-(K),
calcite, fluorite,
gismondine-Ca, baryte and
celestine
(Journal of Geosciences, 69.3.161-172).
Alfredcasparite from Xenolith CS-034 -
Image
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