Ordinary gravel was one of the most common carloadings in the steam era and
HK hoppers were well suited to such loads. Ballast -- as in railroad
ballast -- would likely be (by comparison) relatively small compared to the
need for gravel going into roads, sidewalks, house foundations, anything
using concrete.

The ICC did classify broken stone as a different commodity from ordinary
gravel. I don't know the facts of the situation but going on the names
alone it seems to me that railroad ballast is normally broken stone and what
I've seen going into cement wasn't; FWIW tonnage/carloads of broken stone
reported to the ICC as rail shipments were a tiny fraction of gravel, tho of
course this is only revenue shipments so company MOW wouldn't have been
included. But the take away here is gravel was a very common shipment by
rail.

In the west HK hoppers were also pressed into service during the sugar beet
campaign.

Dave Nelson