Can granite rock record sound?

Question

I heard that granite, being magnetic has the properties to record some vague sound? Is this true?

Answer 1

That's the first I've heard that granite is magnetic. Although there may be trace amounts of accessory minerals which have magnetic susceptibility in granite, such as magnetite, there would certainly not be enough to make the rock magnetic. There are similar rocks such as diorite which may have higher magnetite concentrations - perhaps 1% - but that is far from enough to record sound!

The magnetic intensity of a rock can be the same, higher, or lower, than the surrounding rocks, depending on a complex set of factors related to the polarity of the earth's magnetic field when the curie point of the magnetic minerals was set. If you were to process those variabilities and convert them to sound, then yes you could produce a sound (I'm thinking of the magnetic stripe patterns at the Mid Atlantic Ridge for example) , but the sound is not in the rock. Magnetic minerals in rock lack the hysteresis necessary for them to be altered sufficiently to record a sound.


So the answer to your question is no - granite can not record sound.

Answer 2

Some, but not all, granites contain iron-rich minerals such as magnetite (iron oxide) that are magnetic. When the granite cooled from its molten state, the tiny crystals of magnetite will have alligned themselves with the ambient magnetic field. Now (a) the earth's magnetic field periodically reverses in polarity, and (b) the earths' continents do change their positions over geological time (continental drift & plate tectonics) so by carefully measuring the orientation of these tiny crystals, geologists can extrapolate the past positions of the continents. Other types of igneous rocks that are richer in iron are more suitable for this, such as basalt and gabbro.

But magnetite crystals cannot record sound. Are you confusing this with old-fashioned audio cassette tapes, which I think used iron oxides as part of the recording medium?

Interestingly, granites, when still cooling, or if under tectonic stress, will constantly be fracturing. Boreholes have been drilled into granites and geophones lowered and the actual sounds produced by the fractures can be recorded. But that's quite another subject!

Answer 3

When solidifying it can preserve a record of the Earth's magnetic field. A handy means for geologists wanting to look back at ancient layout of the continents etc

Answer 4

Some people even think this is how ghosts appear, a bit like video tape recordings

All rock has a certain amount of magnatism thats how timeteam use that machine

Answer 5

i think clay can when moving it records sounds as long as the movement is constant

Answer 6

No because there is no place to plug in a microphone.

Answer 7

it's possible, but im saying no