Specimens Svanbergite is a rare strontium mineral. It forms pseudocubic rhombohedrons. The crystals can look nearly cubic, but the angles between the faces are not exactly 90 degrees as is required for a true cube.
Faces tend to be curved and striated.
It forms from the hydrothermal alteration of igneous rocks and in some low grade metamorphic schists. Svanbergite is a difficult mineral to classify in that it has both a phosphate anion group and a sulfate anion group. The phosphate anion group would normally dictate that svanbergite be classified in the Phosphate Class of minerals. But svanbergite's sulfate anion is intricate and essential in its structure, while the phosphate anions can be substituted for to at least a limited degree. Some other classification schemes may place svanbergite in the Phosphate Class however.