Summary: Tlapallite is a new mineral found in 1972 at the Bambollita (La Oriental) mine near Moctezuma, Sonora. Also recently found in old specimens from Tombstone, Arizona. Data for type (Mexican) material: Colour viridian green RHS-128A with pale streak, H = 3, D_calc = 5·05 g/cm³. Crystals monoclinic, class unknown. Indexing based on Ito method gave a cell: a = 11·97 Å, b = 9·11, c = 15·66, β = 90 ° 36′. Strongest lines: 11·972 Å (10), 2·985 (10), 3·540 (6), 5·946 (5), 2·887 (5), 4·731 (4), 3·372 (4), 3·282 (4). Similar data obtain for Tombstone. Chemical analysis for type material yielded the formula H₆Ca₂Cu₃(SO₄)(TeO₃)₄,TeO₆ with Te⁴⁺:Te⁶⁺ = 4:1. However, analysis of the Tombstone material indicates a more general formula H₆(Ca, Pb)₂(Cu, Zn)₃(SO₄) (TeO₃)₄,TeO₆. The better data from this material indicate Z = 4, D_calc = 5·465 vs D_meas = 5·38. Characterized by extreme birefringence, α = 1·815, β = γ = 1·960; for Tombstone α = 1·955, β = γ = 2·115.

Named from the Nahua word tlapalli, meaning paint, in allusion to its mode of occurrence at the type locality.