Unusual Type of Lava? What Do You Think?


I purchased this piece from John Sigfrit near Nampa, Idaho. It was from the collection of his grandfather, Lee Sigfrit, who had passed, leaving the collection to grandson John. According to John, Lee apparently had been involved with the formation of the Peterson Rock Gardens, in Oregon. The collection was largely rough rock contained in piles and multiple drums in John's back yard. But among the rough, there were a number of specimens also, such as Missouri galena, Southern Illinois fluorite, and Bisbee Azurite. This "lava" chunk was one of the larger pieces of this type of material, but there were others. I couldn't tell if it was actually lava, or some kind of industrial slag. If you recognize this piece or have any information on it, please do contact me at This email address is being protected from spambots. You need JavaScript enabled to view it.. Thanks! 


Side view showing a pretty highly vessicular mass that reminds me of a scoria or pumice, and then a less vessicular boundary at the top - possibly faster cooling?

The underside of the piece - pretty frothy but does have some smooth rounded areas. 

Side view close up. 

The vessicular layer, the less vessicular boundary, and the ropey, almost extruded looking strings on top - if not a combination of processes, then at least showing varying rates of cooling. 

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