THE MINERAL SVANBERGITE

Chemistry: SrAl₃PO₄SO₄(OH)₆, Strontium Aluminum Phosphate Sulfate Hydroxide.
Class: Sulfates; although sometimes classified as a Phosphate.
Group: Beudantite
Uses: Only as mineral specimens.
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.

PHYSICAL CHARACTERISTICS:

Color is yellow, rose, honey-orange, reddish-brown to colorless.
Luster is vitreous to adamantine.
Transparency: Specimens are mostly translucent to small crystals being transparent.
Crystal System is trigonal.
Crystal Habits include pseudocubic rhombohedrons and modified rhombohedrons. Faces tend to be curved and striated.
Cleavage is perfect in one direction (basal).
Hardness is 5.
Specific Gravity is approximately 3.2 (slightly above average for non-metallic minerals).
Streak is white.
Associated Minerals include pyrophyllite, kyanite, quartz, topaz, tourmaline, hematite, andalusite and woodhouseite.
Notable Occurrences are limited to Horrsjoberg, Varmland, Sweden; Pomba, Brazil; Quartzite, La Paz County, Arizona; Bluebird Hill, Imperial County and the Champion Andalusite Mine on the western slopes of the White Mountain Peak in Mono County, California, USA.
Best Field Indicators are crystal habit, striations, color, hardness and locality.