A very interesting premise and an unusual and completely different kind of "monster" separates this from other 50s sci-fi/horror hybrids. After narrator Paul Frees tells a little bit about meteorites, one crashes on Earth and explodes, scattering numerous black crystal-like rocks right outside the small Southwest desert town of San Angelo. Geologist Ben Gilbert (Phil Harvey) finds one and brings it back to his lab for analysis. When the rock is exposed to water, it grows and quickly multiplies. And if anyone happens to be around while it's transforming, they too become infected with a disease that spreads through their body like a cancer, turning them to stone. When fellow geologist Dave Miller (Grant Williams, of THE INCREDIBLE SHRINKING MAN fame) returns from a vacation in Las Vegas, he discovers his colleage dead and their lab full of the black crystals. Meanwhile, Dave's school teacher girlfriend Cathy Barrett (Lola Albright) takes her young students into the desert for a field trip. A little girl named Ginny (Linda Scheley) gets her hands on one of the rocks, takes it home and tries washing it. After the rocks are linked to Ben's death, Dave and Cathy go to Ginny's home only to find it in ruins, the parents dead and Ginny's hand infected. She's then rushed off to a big city hospital, where Dr. E.J. Reynolds (Harry J. Cutting) tries to find a cure.
Back in San Angelo, a big thunderstorm saturates the ground, making the crystals spread at an alarming rate. Each crystal grows upward hundreds of feet until it can no longer support itself, then falls over and shatters into hundreds of pieces. Then the process is repeated with each new piece. At that rate, it wouldn't take very long for these things to take over the entire country, maybe even the world. Dr. Reynolds manages to cure little Ginny and relays the information back to Dave, who - with help from former teacher Arthur Flanders (Trevor Bardette) - tries to come up with the right combination of chemicals to stop the quickly-spreading menace before it destroys the entire town.
It was so-scripted by Robert M. Frescoe (who also wrote TARANTULA) and based on a story he co-wrote with pioneering genre director Jack Arnold (CREATURE FROM THE BLACK LAGOON). There's a lot of discussion about sulfur, silicates and saline solutions, but the science talk is kept simple enough to be easily digestible throughout. However, the premise isn't exactly resistent to criticism. Knowing good and well that the rocks have been responsible for several deaths, I doubt you'd see many scientists casually handling these things without gloves. When you factor in their reaction to water, I doubly doubt you'd want to be touching them without gloves in a desert climate where hands tends to sweat. You're also better off not to think too much about what effectively kills the crystals off at the very end of the film.
Though there aren't very many scenes of the "monolith monsters" in action, what is shown use effective and well-done small scale models of buildings and landscapes. The other major special effect of the meteor crash at the beginning of the film was borrowed from IT CAME FROM OUTER SPACE (1953), another Universal production.
The performances are uniformly fine. Les Tremayne has a good co-starring role as a newspaper reporter desperate for a decent story (who finally gets one, obviously) and William Schallert has an amusing cameo as a weatherman. Also be on the lookout for 60s sex symbol Troy Donahue in a (tiny) early role as a guy instructed to blow up a dam.