Specific gravity: 3.608 to 3.508
At the Stubenberg Quarry, Stubenberg am See, Hartberg-Fürstenfeld District, Styria, Austria, pseudosinhalite and magnesiotaaffeite-6N′3S with rare lamellae of magnesiotaaffeite-2N′2S occur as replacement products of spinel in geikielite–ilmenite–baddeleyite–zirconolite veins within dolomite marble. The crystallisation sequence of magnesium-aluminium phases is spinel → pseudosinhalite → magnesiotaaffeite minerals, and spinel formed after or during the replacement of baddeleyite by zirconolite. Pseudosinhalite contains up to 2.2 wt.% TiO2, 1.4% Cr2O3, and 1.3% FeO. The replacement of spinel by pseudosinhalite, a magnesium-aluminium borate, requires an influx of boron, since no boron-bearing minerals are present in the original assemblage (CM 46.1195-1205).
At the type locality, the Tayezhnoe Fe-B skarn, Aldan, Sakha Republic, Russia, pseudosinhalite is a rare mineral in a contact-metasomatic boron-rich iron deposit, a product of retrograde alteration of sinhalite in magnesium-bearing skarn. Associated minerals include calcite, dolomite, forsterite, green spinel, ludwigite, warwickite, suanite, clinohumite, szaibelyite, brucite, sinhalite and hydrotalcite (AM 84.1196-1197, HOM).
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