I am a fabricator.

The netting on the back of the stone is done to provide some additional mechanical integrity for stones that are more easily cracked or broken. These stones are somewhat more of a challenge to the fabricator but a non-issue for the end user.

Today many slabs are resined at the factory. Many stones, when polished, have very small (too small to feel with a fingertip) "pits" that are visible when the stone is viewed with certain lighting and viewing angle. This makes the stone less valuable commercially because the public expects the stone to be glassy smooth.

The resining process impregnates a very thin layer of resin into the stone BEFORE polishing. Once polished the "pits" are gone because the resin fills them. The actual resin layer is very thin; less than a 1/10 of an inch.

Resined slabs can often be identified easily in the slab yard by looking at the edges of the slab. You can see "drips" where the resin overflowed the top of the stone and left a residue on the edge of the slab. (This would not be true for slabs with sawn edges as the rough outer edge with the residue will have already been sawn away.)

Resined stone can create one challenge to the fabricator. Lighter stone will be slightly darker when resined which can make the polished edges noticably lighter. A competent fabricator is aware of this and uses a product during finishing that darkens up the edges enough to match the resined top surface.

Resin does not "come off". Your stone supplier was probably right when he showed you a large area of fill and said that was most likely what someone was talking about.

Resined slabs, because the very top of the stone is impregnated during the resining process typically would not need to be sealed.

To reinforce Oldryder's statements, don't be alarmed to see netting on the back, it's very common.

Most stones have resin applied during the polishing process, the resin is ground off when they complete the final few grits of grinding/polishing. There is no resin left on the surface, it just fills imperfections.

Although in theory, resined slabs should not need an impregnating sealer applied, in reality many resined stones still may need to be sealed.

Thank you so much for your replies. I feel I don't need to stress so much any more. I feel better about the resin now.
I was just reading a post "help me choose a quartzite for my island" posted by socom. She posted pictures from the stone yard of three quartzite slabs. I noticed that only one has the backing and the sides finished off. So my question is why would only that one have it ? Is that due to the preference of the supplier to protect the stone or do they use that backing only on specific stones? I think I have seen the backing before but not how the sides are finished off.

Thank you for taking the time to explain everything.

When looking with my son at slabs for their kitchen, I noticed that more slabs had backing then when we did our kitchen (around 2006). Also I saw quite a few of the totally even edged slabs you describe (which look quite odd when used to the sliced off the block and polished uneven edged slabs). There weren't any of those when we did our kitchen. It seems likely that both are mostly due to changing the way slabs are produced rather than slabs getting more fragile.

Some times it seemed that some of the more expensive stones had that squared off and net back treatment so perhaps it is being done to protect an expensive stone in some cases rather than because the stone is particularly fragile.

Our quartzite slab (in 2006) was resined but didn't have a net back. The resin hasn't caused any problem.