This is a dense gravel. 3/8" angular pieces. It's called chip seal. It is installed over asphalt, with the typical subbase that asphalt is installed on. The asphalt it then covered with a tacky asphalt liquid. Then the rocks are spread over. Some stick, some don't. That give it a rural, country look. As for cost, in Santa Barbara, probably $5-7. per foot, in any other part of the country, likely about 1/2 that amount. Not sure how the durability is in colder climates.
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