Sveite [KAl7(NO3)4(OH)16Cl2·8H2O] first described from Venezuela and material recently collected from northern California have similar X-ray diffraction patterns and chemical compositions. The main difference in the chemical composition is the absence of significant chlorine and sulfate in the sveite from California. The changes observed by X-ray diffraction upon hydration and the SEM images of the crystals suggest a layered atomic structure. Water-extractable NO3 in the Venezuelan sveite sample is isotopically enriched in δ15N and δ18O and likely was affected by the microbial process of denitrification. In contrast, the extractable nitrate from the California sveite is less isotopically enriched than the Venezuelan mineral and there is only modest evidence that denitrification had affected its isotopic composition. Overall, the nitrate in the California sveite is isotopically similar to nitrate present in acidic soils overlying the mineral occurrence, suggesting a general biogenic source of uric acid from bird feces for the mineral-bound nitrogen.