The most captivating mental image for me in Lovecraft was where the sailor got trapped crossing what appeared to be an obtuse angled surface that was actually acute, stuck and perhaps crushed to death in this invisible chasm, in the non Euclidean metropolis, or necropolis, of R'lyeh.
However the Starry Wisdom Cult and the Esoteric Order of Dagnon with its unusual clerical vestments were of much interest in the realm of comparative theology. Although his mentioning of the Yazidis was uninformed and came across as a theological cheap shot, although there is evidence to suggest that in the past some Yazidis were genuinely afraid of Taus Melek, adding credence to the whole Decil Worship thing.
But these crystals aren't quite as non Euclidean as what Lovecraft had in mind I fear. Although I suspect they would freak him out anyway, poor guy.