Adair
You're assuming all gravel is the same or that I am using crushed granite gravel. You've never seen gravel mined from around here (Long Island) have you?
This isn't crushed gravel mined from a granite quarry, its pea gravel sorted from sand mines around here.
Long Island is a terminal moraine from a glacier, the rocks experienced lots and lots of grinding from sand, other gravel, rocks and ice as it got pushed by the glacier.
It isn't granite "grit" or crushed gravel. It is predominantly quartz and its mostly round and fairly smooth, not jagged and pointy.
In fact, the lava and pumice are, on average, both more angular and pointy than the gravel and were purchased from a well known bonsai supply company as a mix.
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