Steiningerite

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Formula: Ba₂Zr₂(Si₄O₁₂)O₂
Valence: Ba₂Zr⁴⁺₂(Si₄O₁₂)O₂
Cyclosilicate (ring silicate), barium-bearing mineral
Crystal system: Tetragonal
Specific gravity: 3.78 calculated for the empirical formula
Hardness: 3½ to 4
Streak: White
Colour: Colourless or creamy white
Luminescence: Weak orange fluorescence under short wave UV (λ = 254 nm)
Solubility:
Common impurities: minor K (replacing Ba), Ti (replacing Zr), F (replacing two of the O atoms)
Environments

Volcanic igneous environments

Steiningerite is a new mineral, approved in 2024 and to date (January 2025) reported only from the type locality.

Localities

At the type locality, Löhley, Üdersdorf, Daun, Vulkaneifel, Rhineland-Palatinate, Germany, mineral assemblages are found in cavities, fissures and pegmatite-like veins within the host melilite nephelinite. The Löhley quarry is the type locality for four other mineral species, batiferrite, noonkanbahite, schüllerite and lileyite.
Steiningerite from the Löhley quarry occurs in fissures filled mostly by colourless isometric leucite crystals, dark green tabular clinopyroxene and black isometric perovskite, whose sizes are all a few mm. Minerals of the pyroxene group are represented mainly by augite and diopside. Locally, brown elongated crystals of titanite and yellow tabular crystals of fresnoite also are present. Fluorapatite, wöhlerite, götzenite, fersmanite, magnetite and minerals of the pyrochlore group, primarily fluorcalciopyrochlore, are noted as accessory phases.
Steiningerite crystals typically exhibit a euhedral, short prismatic to thick tabular, partly pseudocubic habit. The maximum size of individual crystals in the holotype specimen reaches 0.5 mm, although crystals of this size are relatively rare; in general, steiningerite crystals are smaller, and their size does not exceed 100 μm. In most cases, steiningerite crystallised on isometric perovskite crystals (possibly as epitactic overgrowth) or in immediate contact with them. Occasionally, steinbergite is also observed on leucite crystals. Steiningerite is transparent to translucent, creamy white or colourless, with a vitreous lustre and white streak (MM 89.819–829).
Steiningerite from Löhley - Image

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