Granite is a natural stone, and thus, often doesn't match exactly even within one slab. Be prepared for a bit of variation, but trust this new company to have the capability and customer care culture to do a good job for you. Try not to be too suspicious of them despite your bad experience with the other company.

It depends . . .

Since Granite is the result of magma cooling & the coloration is a result of randomized chemical reactions to that cooling process that means granite has a completely random pattern.

In short if you took a single slab of granite, and cut it in half, those two pieces would not perfectly match each other. (The cutting blade would remove a fraction of material, and destroy the continuity of the previously single slab). So even the same piece of granite abutting itself will not match perfectly!

On the other hand, granite is formed in huge chunks and its it mined & shipped in layers. The supplier may actually have a very similar piece of granite from the same quarry that will look almost indistinguishable, when abutting your existing granite.

It also depends on the purpose of the smaller piece of granite.

In short, the odds of the replacement granite not matching is absolutely 100%. But the replacement piece may be indistinguishable from the rest of the pieces.

The other question is, how are these two pieces abutting?

Thanks so much for the feedback. When I say they are abutting - what I mean is that the original slab in the first installation was L shaped and very large, and had the sink hole in it. They broke the granite on both sides of the hole. This large L-shaped piece had to be replaced. My kitchen is a U shape and this piece was one of two that covered the entire expanse and originally there was only one seam (their choice, not mine!). The second installation, they came back and replaced the L with two new pieces of granite from the original lot - the larger piece contained the sink hole, and the other piece was small and completed the original L shape and is positioned exactly opposite the unbroken original piece and creating a second seam. The sink piece sits between a large peninsula piece and this smaller piece. The smaller piece is cut too small and needs to be replaced so the entire countertop (the entire U, not just the one side!) can be pushed back against the wall and eliminate the gap between the wall and the countertop that they "hid" beneath the backsplash. I can stick my entire finger in the gap on the peninsula side. There are two additional pieces of granite that stand by themselves and are installed perfectly. They all "match" perfectly - color, amount of gold flecks interspersed, and are absolutely beautiful. I am hugely skeptical that I will be bothered less by mismatching granite patchworked in than by huge gaps. I proposed that they buy the original broken granite piece from the first subcontractor to replace the piece that needs to be replaced and I know matches and is from the same lot, or that they redo the countertops with all granite from the same lot (which will be so wasteful and will make me sick - but will ensure that I get the quality that I payed for) - or that they just fix the backsplash (which overhangs the peninsula piece by a bit more than a 1/4"!??) and be done, and refund most of my money. Their solution is to educate me about lot numbers and cut numbers in the beginning of the process, and then suddenly decide that all that doesn't matter and they can just eyeball the match when a piece needs to be recut and replaced.

This story really makes me uncomfortable.

This sounds like series of professional mistakes and while the contractor is facing a huge loss due to the mistakes, it doesn't change the fact that you ultimately are not receiving the product and services that you paid for. My guess is that the contractor is trying to implement a substandard solution to cut his losses.

Here's my ultimate thought based on your full description; I'd recommend that the contractor replace the whole batch. They should have general liability insurance to cover their losses.

You should also not trouble yourself on the material waste. The pieces may be useful for another client or could be repurposed for other needs.

That is what has been my nagging suspicion too. Thanks so much for taking the time to comment! I am in the dark here, and am glad to have your expertise!