For evidence of that mineral abundance, look no further than Irwindale, home to more than a dozen massive pits emptied last century for those critical building components.

But now, as another building boom rumbles across Los Angeles and a new generation of high-rises climbs skyward, the rock and sand are coming from a much more distant source: Canada’s Vancouver Island, more than 1,400 miles away.

That’s a long distance to ship commodities that are still abundant locally, sell for less than $20 a ton — and often cost more to transport than to mine.

Yet thanks to a combination of materials science, cheap ocean shipping and, some argue, NIMBYism, today’s industrial concrete mixers are often filled with imported rock and sand.

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