Magnetic rocks

Has anyone seen or have examles of basaltic andesite that atracts a weak magnet easily ? The images show two examples a small weak magnet sticking to basaltic andesite, ive found that this area of Dyke is far more magnetic than other outcrops.

It's not too uncommon to have abundant magnetite in basalts and andesites, but it usually takes a good magnet to stick.

Regards,
Ralph

Ralph i use a small piece from a fridge magnet about 10mm widest 3mm thick, it sticks well, i was initially told by a geologist from a local university that what i must be finding was whin sill that had been transported from the north and north west, ive proved this not to be the case, and that it is as i first sugested basaltic andesite from the dyke in this area, ime still waiting for a reply.



Edited 1 time(s). Last edit at 05/17/2012 07:22PM by Heath Barnes.

This isn't so unusual, many of these rock types have either magnetite or chromite inclusions.

Spencer Ivan Mather Wrote:
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> This isn't so unusual, many of these rock types
> have either magnetite or chromite inclusions.


Thanks Spencer do you have any trustworthy images of a small weak magnet sticking to rocks other than loadstone as i can't and boy ive tried, i would love to find an image of a simmiler magnet stuck to basaltic andesite, there has been lots of papers refering to compas deflection but ime yet to find one that refers to a magnet actually sticking to it!

Hi Heath, Sorry but I don't have any images of a magnet stuck to a piece of these rocks, as far as I know magnets won't stick to these rocks as the rocks don't have enough of the material that is atracted to a magnet.

Spencer.

Spencer ive found tons of basaltic andesite and as yet unidentifyed rocks that all easily atract a small weak magnet, all from the area ime working in its been reported to the powers that be but ime yet to get an explanation, i think i may have found a conection between how this basaltic andesite reacts to a magnet and the period of reversed polorization the earth was in at the time the dyke was active.

"i think i may have found a conection between how this basaltic andesite reacts to a magnet and the period of reversed polorization the earth was in at the time the dyke was active."

???

Spencer its in short that the basaltic andesite is only atracted to certain sides of any one magnet, i am in no way qualified enough to make statements of fact as i may be wide of the mark, there is more that has me believing there maybee a conection but i will leave it at that untill ive had the on site help ime hoping for in the near future.

Heath, unless you have several dykes in close proximity, emanating from the same source location, showing changes in polarity from one to the next, you would be very unlikely to be able to tell the earths polarity at the time of their forming, let alone the reversals in the earth’s polarity.
I would suggest you read up on paleomagnatism to better understand the way the earth has undergone changes in polarity over time.
What the polarity of your dyke most likely shows is the movement of the tectonic plates in relation to the poles from the time the dykes forming through to today.
ie: a magnet placed on the dyke today, may point east-west, rather than north-south, this would show that at the time the dyke formed it was facing approx 90deg different to it’s current facing.
This change of direction is most likely caused by tectonic movement.
Other possible causes are; local movement in relation to earthquake(s) or movement in relation to local rock forming processes.
The difference between the current polarity of the dyke and polarity of the earth would in no way be related to paleomagnatism.

Cheers Mark.

We will never have all the answers, only more questions!

Thanks for that Mark ime still trying to get my head round all you stated, i was given a link from a man of science from the us i can not find it to resize at the moment but it showed that the Cleveland dyke and many more that origionated from the same ocurance in the north west of scotland as we know it now, that the earth was in a state of reversed polorization at the time. ? I trust the info as ive been in contact with the man for some time and he is a respected individual.
Also you obviously know your stuff so could you do what no one proffesional or amature have managed yet, give me images of weak magnets attatched to basaltic andesite ? in the manor i have show on many tons of the stuff, the only other reference i have is rosedale iron stone funny enough not far south of here?

Cheers Heath.



Edited 1 time(s). Last edit at 05/17/2012 07:26PM by Heath Barnes.

After going through this post ive noticed two things, 1, people may well think ime some sort of would be indiana jones! please dont mistake my enthusiasum for anything like that, ime just a common man looking for answers. And as yet on this subject i have none, i have had 3 geologists involved so far and still don't have an explanation. And 2 still no images of weak magnets stuck to rocks other than loadstone, i find a lot of amatures and proffesionals when commenting on this subject, allways state how common magnetic rock is withought either realising or forgetting to mention that yes a lot of rocks have magnetic properties, ie will deflect a compas needle, but will not attract a weak or indead strong normal magnet.