Three new alluaudite-like protonated arsenates: NaMg<SUB>3</SUB>(AsO<SUB>4</SUB>)(AsO<SUB>3</SUB>OH)<SUB>2</SUB>, NaZn<SUB>3</SUB>(AsO<SUB>4</SUB>)(AsO<SUB>3</SUB>OH)<SUB>2</SUB> and Na(Na<SUB>0.6</SUB>Zn<SUB>0.4</SUB>)Zn<SUB>2</SUB>(H<SUB>0.6</SUB>AsO<SUB>4</SUB>)(AsO<SUB>3</SUB>OH)<SUB>2</SUB>