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Are there any Nitrate salts that are generally insoluble in water at room temperature? Textbooks are generally vague about this. They say that all nitrate salts are mostly soluble in water, or that there are "few exceptions". I understand that insoluble doesn't mean 0% of solute dissolves, and I also understand that when something is soluble, that doesn't mean it is 100% soluble under normal conditions. I just want to know if any nitrate salts exist that are relatively insoluble in water at room temperature. Also, when I say "exist", I mean it occurs naturally and is relatively stable.