Hardware and Fasteners - Fasten to stone or mortar?

I need to install an electric box on a stone wall for a medium heavy wall lantern.

Is the stone or the mortar the most secure place for the anchors?

What kind of fastener?
Thank you

You will have to put the anchors in mortar.Anchor choice would be dependant on weight,number of anchor points,screw size and hole in fixture size etc.

If you could even drill a stone,which is doubtful,you might break it apart etc.

Your choices range from plastic anchors to tapcon screws to lead anchors.You'd be smart to take either the whole fixture or the mounting part(s) to a hardware store so you can work with saleshelp and try out various possibilities.

How deep is the substrate? If this has a wooden frame, you probably have at least OSB for a wall stiffener. I would try to get a fastener to go through the joint and into the OSB for a solid hold. Otherwise, the tapcons and other mechanical means are on target.

Thank you for replies,unfortunately there is no frame , the wall is made of double cinder blocks and the stones on the outside,I open a hole on the porche's ceiling to run the wire there is a big a big chunk of cement on top of the blocks so I need to find a way to drill down on this cement and horizontal through the mortar and blocks to run the wire to the box.
If the box is fasten to the mortar I can use two or four screws depending on location.The fixture is fasten to the box
Thanks again