What can you use to fix a marble fire surround to the wall?
There are steel brackets (electro-brassed) available at B&Q,
They have 3 holes two for securing to the marble, and the other pokes out the side so that it can be affixed to the wall with a rawlplug and countersunk wood screw. I have seen them used to secure heavy mirrors. As you intend securing marble it would be necessary to carefully masonery drill the back of the marble, insert a plug and secure with a screw,also using epoxy adhesive as a belt & braces approach.
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antique farm table