Jane McGary janemcgary@earthlink.net
Fri, 15 Oct 2004 17:26:20 PDT
Rodger Whitlock wrote,
Everybody interested in pumice should be aware that the stuff sold
>for landscaping is not necessarily pumice. I have several bags each
>of black and red "volcanic cinders"; these are not pumice, but
>others might mistake them for pumice because of their volcanic
>Volcanic cinders (for which there is undoubtedly a technical term)
>are little blobs of lava that were thrown into the air and hardened
>before landing. They are dark, have sharp edges, and are definitely
>not "frothy".

the technical term for this material is "scoria." Loren Russell, an 
excellent rock gardener, swears by what is locally called "red rock" (red 
scoria, loosely red pumice) as a nutrient-rich material, and incorporates 
the dust and fines from piles of it (which are sold as a mulch) in his 
planting mixes.

Jane McGary
Northwestern Oregon, USA

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