Basaltic lava caves are important Earth analogs in our search for life on Mars and other planets. Terrestrial lava caves exhibit morphologically diverse secondary mineral deposits (speleothems) often associated with liquid water. The detailed geochemical characterization of cave water and speleothems can provide valuable insights on potential biotic or abiotic mechanisms that lead to formation of these features. Our results showed that the cave water chemistry is consistent with basaltic host rock chemical composition. The water contained high levels of dissolved organic carbon and nitrogen, which could support microbial growth. The dissolved organic matter showed macromolecular structure and appears to be plant-derived, highly humified and microbially processed. Elevated nitrate in cave water may be due to agriculturally influenced regional surface water source or in situ oxidation of ammonia or organic N. Speleothems contained 29-79 wt% of crystalline, cryptocrystalline, or amorphous SiO2, and secondary minerals containing biosignature elements (Ca, Mg, Fe, Mn, S and V). This work complements the ongoing NASA BRAILLE (Biologic and Resource Analog Investigations in Low Light Environments) project to study basaltic lava tube caves as Earth analogs and ultimately provide insights for planning future missions to search for biosignature on Mars and other planetary bodies.