I was playing in my newly generated world. I had decided to go below y=0 for the first time. I wa also excited and I finally found a cave bellow y=0.... but sadly no ores had generated. I searched and searched and there was only regular stone below y=-2. I then found another cave at y=0, and finally found some ores. But then I realized once I went bellow y=-2, all ores and gravel, dirt, andesite, etc., all stopped generating. All there is is stone.