EVEN ON FILM, far removed from its first-hand visceral impact, Michael Heizer's "Levitated Mass" is an impressive work. A 340-ton chunk of granite, it sits outside the Los Angeles County Museum of Art (LACMA), held up by two flimsy-looking steel shelves, floating ominously over a trench. A trench you can walk under, if you happen to be in Los Angeles, and happen to want a better look at what 340 tons of granite looks like over your head and under sunlit smog, and happen to feel like having an existential revelation about how little your life matters when compared to a goddamn rock.

Or if you want to have any other revelations, I guess—if there's one thing Heizer's aggressive, rugged sculptures prove, it's that there's no shortage of ways to interpret them. Arguably Heizer's most ambitious work (at least until he unveils his sprawling "City," which he's been constructing in secret, in the remote Nevada desert, for the past 40 years), "Levitated Mass" cost $10 million, required a small army to complete, and came with a few extra tons of legal, financial, and bureaucratic concerns. Levitated Mass, director Doug Pray's film about Heizer, LACMA, and "Levitated Mass," digs into them—and doesn't shy away from the concerns people have about the work itself, either. "I think it's nuts! A rock?!" says my favorite cranky old lady ever. "Sounds kinda dumb."

It is kinda dumb, but it's other things too: awe-inspiring, weird, and—intentionally or not—a Pandora's box of social and privilege issues. Unexpectedly, Levitated Mass works best when it focuses not on the rock or on the terse, leather-skinned Heizer—but when it focuses on the Californians, from blue-collar quarry workers to small-town bystanders, who come into contact with the towering hulk of granite as it's slowly transported past their homes on a gargantuan rig, while tiny men in hardhats and safety vests scurry beneath it. For example: Even if LACMA goes out of its way to note that the $10 million was privately funded, that doesn't buy a whole lot of goodwill when some residents of South Central see the rock rolling through—and who, looking around their neighborhood, can come up with far more pragmatic ways to spend $10 million.

Levitated Mass NW Film Center's Whitsell Auditorium, 1219 SW Park, Sun Oct 5 at 2 pm, Mon Oct 6 at 7 pm, $9