I once heard the following story. I am sure it has no scientific value what so ever, I can find no reference online but i like it.
In Cardiff in the late 70's there was a building which was said to be haunted, at certain times, strange voices could be heard emanating from the walls. The walls were fashioned from very old stone.
A meeting was being held in the building one evening, and the strange voices started, a visiting professor of Welsh histrory from Aberystwyth., recognised the voices as those of ancient Welsh speakers.
It turns out that the walls were made from sandstone, and thus had a high proportion of silicon, this was acting like a silicon chip and had recorded voices under certain conditions. When similar conditions of moisture and heat occurred the voices could be heard coming from the stone.