Newbie, needs help on the choice of a detector

[paranal]

I have a plan to search for a stone ON the ground which is rich in iron. But I can't locate it exactly. The area I want to detect is about 4 square kilometers. What I need is a large-scale detector to scan line-by-line in this area, so I wonder which type has a appropriate detecting range to meet my needs.
In addition, I want to know how many square meters the scan-scale of normal metal detector is.
Just thanks.

 

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[Sandman]

You gotta be fooling us, Right? A stone on the ground? Unless it has Iron in it, forget it. If your stone has the iron in it, you'll need a detector that searches in all metal. That's a lot of territory to search too and it could take you years. The search field of todays detectors is measured in area and this is about the width of the coil and a depth of about a foot on a coin size target. These things don't point to where something is, you have to put your coil over it. With hot rocks this also will slow you down.