Chief C -

I haven't found a lot of information about the filter material. It apparently was originally "mined" from mineral deposits, but now seems to be mostly "manufactured" using industrial methods and starting from basic chemical components. There are a variety of uses, and it's apparently the structure of the grains that has much to do with how a particular material behaves, although chemical composition is of course important.

A problem with the natural "mineral product" was that a desired structure could be obtained only by filtering and sorting to separate the different grades/kinds that occured in the raw product; but methods now can (sort of) make-to-order a fairly specific product.

Even the term/name may be sort of a stretch for the currenly most used products, since the pore sizes (basic to the performance) are now produced by controlling process rates rather than by leaching out the diatoms to create pores in a sediment. Many reports do call the filter media just "zeolites" and that's possibly a more accurate name for the current products.

Grain/pore sizes for most purposes are quite small, but probably not legitimately what could be called "nanoparticles." A lot of the current "buzz" about nonoparticles probably does have a heritage back in the study of how structure and size affect chemical behaviour, as was/is being done for materials of this type.

John