here's a photo for folks to see

This looks like a filled repair to me. Does the lighter blue in the blotch have the same gloss as the surrounding material?

Definitely no stone expert here, but that TOTALLY looks like a big ol' crack.

A naturally occurring fissure or "no fault crack" would typically be where two swirls of stone meet ... at a natural discontinuity in the material. It's a weak spot for those gaudy dramatic stones.

This looks like it's cutting pretty straight across, like a post-manufacturing stress crack. Those can take a while to show up.

Were the cabinets checked for level? And well-braced? Has the floor sagged? Have the cabinets warped?

Hi,
Thanks all for your responses.
To answer Lazygardens, the island is perfectly level and extremely well braced and solid. The floor is not moving. It has porcelain tile beneath it all which is rock solid...no cracks. I noticed this "fissure" as the installation manager calls it the day after the install. I can post a more detailed, painfully long letter I intend to send to the installation manager's boss of how they assessed the situation.

again, Thanks much

Hi,
Thanks all for your responses.
To answer Lazygardens, the island is perfectly level and extremely well braced and solid. The floor is not moving. It has porcelain tile beneath it all which is rock solid...no cracks. I noticed this "fissure" as the installation manager calls it the day after the install. I can post a more detailed, painfully long letter I intend to send to the installation manager's boss of how they assessed the situation.

again, Thanks much

To answer trebruchet, the gloss is the same in the "blotch" as all around it. Nothing looks filled at all. To answer another question of Lazygardens, as I wrote in my description, this disruption cuts mostly indiscriminately through homogenous compositions as it runs it's course and occasionally goes between some areas where different compositions meet. I think in the latter case, as stated above, I think it does this because there might be points of less resistance in those areas

To answer trebruchet, the gloss is the same in the "blotch" as all around it. Nothing looks filled at all. To answer another question of Lazygardens, as I wrote in my description, this disruption cuts mostly indiscriminately through homogenous compositions as it runs it's course and occasionally goes between some areas where different compositions meet. I think in the latter case, as stated above, I think it does this because there might be points of less resistance in those areas

My mom's typhoon bordeaux has a line in it that looks like a crack or fissure. I was sick when I saw it and wondered the same as you if it was a crack or just a fissure. I was able to see the underneath side of the granite by taking a drawer out to see if there was the same line on the underside which would pretty much insure it was a crack. Is there any way you can view your granite from the other side?

I am a fabricator.

If the fissure or crack proceeds down the edge of the material and it can be snagged by a fingernail then I'd call it a crack. At a minimum I'd expect a warranty from the fabricator against it becoming worse over time. A skilled fabricator or stone repair person could probably make it much less prominent.

Iif it's an overhang it should be rodded which you could see by inspecting the underside of the exposed area.

Unless he had no other option a good fabricator would've avoided such a prominent negative feature. In my shop at a minimum we would have shown the customer that feature before sawing the slab.

That stone may be a tad more fragile than others.
That is a crack possibly along a weakness in the stone.
It needs to and can be repaired using the proper adhesives and techniques.
I agree with old ryder.
Is this the way your stone was delivered?
It could have happened during installation.
If you cant get the fabricator back or they aren't qualified to repair this you may need to hire a stone refinisher experienced with this type of repair.
This is not an easy repair.The material is resined and the damaged area will need to be leveled and re-polished blending in and matching the original finish.