I mentioned in one of my earlier ride reports that in some places here the roads sometimes sparkle in the sun. I postulated some sort of quartz rock in the aggregate. It seems the explanation is more mundane but still quite interesting.
One way of recycling glass in this country where vast distances make many forms of recycling uneconomic, is to grind up the glass and add it to the road metal (or gravel as they call it here) used as aggregate. Everyone can use a supplement to road metal.