Villain(s)  Growing meteorite fragments

Actor(s):  Grant Williams, Lola Albright, Les Tremayne, William Schallert

Brief Description  The Monolith Monsters (1957) is an American black-and-white science fiction disaster film produced by Universal-International. The movie stands out among 1950s creature features because its "monsters" are completely inanimate: giant, fast-growing alien crystalline rocks that expand upon contact with water. Instead of a radioactive beast or a humanoid alien, the threat is a purely ecological and chemical chain reaction that crushes everything in its path.

Plot:
The Meteoric Arrival: The film opens near the sleepy, isolated desert town of San Angelo, California. A massive meteorite crashes into the desert and explodes, scattering hundreds of unusual, jet-black fragments across the arid landscape. Government geologist Ben Gilbert finds one of these heavy, glassy fragments and brings it back to his office for analysis. That night, a routine desert wind knocks over a water pitcher on his desk, soaking the rock.

Discovery and Petrification: The next morning, head geologist Dave Miller returns to the office to find the building completely destroyed—shattered outward as if pushed by an enormous force. Inside, he makes a horrifying discovery: Ben Gilbert is dead, and his body has been completely turned into solid, calcified stone. Meanwhile, schoolteacher Cathy Barrett takes her students on a desert field trip. One of her students, a young girl named Ginny Simpson, pockets a small piece of the black meteor rock to take home. At the Simpson ranch, Ginny uses a bucket of water to wash the rock.

The Threat Multiplies: Dave investigates the destruction alongside the local doctor and Professor Arthur Flanders. They rush to the Simpson ranch after hearing reports of trouble, only to find the farmhouse crushed by massive black rocks. Ginny is found alive but is semi-catatonic; her arm is rapidly turning into solid stone. Dave and Professor Flanders realize the terrifying truth: the alien crystals absorb silica and moisture from whatever they touch, including human flesh, causing a petrification disease. They rush Ginny to a medical facility in the city to find a cure.

The Thunderstorm and Geometric Growth: While scientists try to save Ginny, a massive desert rainstorm breaks out over San Angelo. When the thousands of fragments lying out in the desert absorb the rainwater, they begin to grow exponentially. They swell into towering, skyscraper-sized obelisks. Because of their immense height and weight, the monoliths reach a breaking point, top over, and crash violently into the desert floor. Upon smashing, each giant pillar shatters into thousands of new fragments. As the rain continues, every single new fragment begins to grow into another giant monolith, repeating the cycle in a geometric, unstoppable march toward San Angelo.

The Scientific Solution: As the literal mountain of moving stone prepares to crush the town, Dave and Professor Flanders work tirelessly in the lab. They discover two vital things: The petrification in humans can be halted using a special serum that counteracts the loss of silica. After experimenting with various chemical compounds on the rocks, they find that saline (salt water) completely inhibits the crystals' growth by blocking their chemical reaction.

The Climax at the Dam: The monoliths are steadily advancing through a valley directly toward the town. Dave realizes they do not have enough salt in the lab to stop a mountain. However, he remembers that a massive commercial salt mine sits at the head of the valley, directly below a large mountain dam. In a race against time, Dave and the local authorities evacuate San Angelo. Dave risks his life to plant dynamite at the dam. He detonates the explosives, releasing millions of gallons of water that flood through the salt mines. A massive wall of highly concentrated salt brine rushes down the valley, washing over the advancing front of the monolith monsters. The reaction is instantaneous. The saline solution neutralizes the rocks, permanently locking them into safe, non-growing formations. San Angelo is saved, and humanity is spared from being buried under a mountain of alien stone.