Chlorapatite (pentacalcium triarsenate chloride), Cas-(AsO4)3C1 crystallizes in the hexagonal system and is closely related to its phosphate analogs, Ca5(PO4)3X (X = Cl, OH), but has a slightly modified structure in terms of anion sites.

Nonaniobium arsenic pentacosaoxide contains 3 × 3 ReO3-type NbO~, octahedral columns extended along c. Each column is linked to four crystallographically identical columns through shared edges of NbO6 octahedra and shared corners of AsO4 tetrahedra.