A lovely barite from the Linwood Mine, located in the Midwestern state of Iowa.  This piece consists of a cluster of multiple single and doubly terminated crystals, with a single larger, terminated crystal thrown into the mix.  Some faces are lustrous, others have bits of sediment that give a more matte finish. 

Although not particularly well known outside the US, the Linwood Mine has produced some of the country's finest (and certainly largest) barite crystals, though it had not received the same attention as Elk Creek (South Dakota), the various Colorado localities, or the Meikle Mine (Nevada).

This piece comes from a find made within the last year and a half.  

Opened in 1944, the Linwood Mine is an active producer of calcium carbonate products, which are used in glass and plastic manufacture, cements and other building materials, feed, water purification, and various other chemical applications.  Given the high purity of product necessary for such uses, the presence of these barium sulfate crystals is actually considered a bad thing--when crushed into the mix, they become contaminants.

The site was originally operated as a quarry, though is now an underground mine.