Yes, it is generally dangerous to microwave a rock. Rocks, especially those with high mineral content, can contain pockets of water or other volatile substances. When microwaved, these pockets can heat up rapidly and potentially cause the rock to explode or shatter, leading to fragments and hot particles being ejected from the microwave.
The rapid heating of the rock can create uneven expansion, causing stress and structural weaknesses within the rock. This can result in the rock violently breaking apart, posing a risk of injury to anyone nearby and potentially causing damage to the microwave.
In addition to the risk of explosion, microwaving rocks can also damage the microwave oven itself. The intense heat generated by the rock can cause arcing or sparking inside the oven cavity, potentially damaging the interior walls, turntable, or other components.
It's important to note that microwave ovens are designed for heating food and beverages, not for heating or altering rocks, metals, or other non-food items. It is advisable to only use a microwave for its intended purpose and follow the manufacturer's guidelines and safety instructions to avoid any hazards.