From Ohio History Central

The name halotrichite comes from the Latin meaning "hairy salt," hence the German common name of Haarsalz. Pickeringite was name after J. Pickering (1777 - 1846). Although they contain varying amounts of iron and magnesium, members of the halotrichite-pickeringite series have similar physical properties. In halotrichite, the iron content exceeds that of magnesium. In pickeringite, however, the magnesium content exceeds that of iron. Lacking specific chemical data, specimens generally are identified as members of the halotrichite-pickeringite series.


Chemical Composition:Iron Alum (Fe,Mg)Al2(SO4)4•22H2O - Magnesia Alum (Mg,Fe) Al2(SO4)4•22H2O
Mineral Class:Sulfates
Crystal Habit:Commonly found in fibrous aggregates.
Specific Gravity:1.8 - 1.9
Hardness:1 1/2 - 2
Color:Generally white, but may be yellowish white, reddish white or greenish white.
Transparency:Transparent to translucent
Luster:Vitreous to silky
Occurence:<img width="195" height="172" title="Map of halotrychite-pickeringite occurence" alt="Map of halotrychite-pickeringite occurence" src="images/naturalHistory/minerals/halo-pickmap.gif" />


The halotrychite-pickeringite series has been reported from 8 counties in Ohio.In central and eastern Ohio fibrous efflorescences of this mineral series commonly are associated with pyrite in shale or coal. Geologists believe that the halotrychite-pickeringite series will be found in more places in Ohio than those shown on the map above.


  • Carlson, Ernest H., ed. Minerals of Ohio; Ohio Division of Geological Survey, Columbus, OH; Bulletin 69; 1991.
  • Pough, Frederick H. A Field Guide to Rocks and Minerals; Houghton Mifflin, Boston, MA; 1976.
  • Sorrell, Charles A. Rocks and Minerals; Golden Press, New York, NY; 1973.

See Also