[Anvh]

I would return it if you can't simply clean it like has been said, this lens isn't mint like advertised, it's as simple as that.

[mikeSF]

I would definitely ask the seller for a partial credit or return it for a refund if there was no mention of the mark.

...
Dust on a lens isn't going to affect it's picture taking ability unless there is a ridiculous amount accumulated

i respectfully disagree with this statement. When shooting sunrises, sunsets, or strong oblique light, sometimes even the slightest bit of dust particles can light up and make little spots on the image. I've seen this far too often to disregard and whenever i know i'll be shooting into the sun, i check my front element thoroughly and blow off dust. Similarly, cleaning scratches can also light up in strong light and cause flares. For all other shooting, such light dust is probably unnoticed in the image, so i agree with you on that. I always use a hood as well.

... in which case a soft brush or compressed air/canned gas is a better way to remove it.
Also, a well washed old t-shirt is one of the best fabrics for cleaning lens glass if smudges have to be removed.

i wouldn't dare touch a T-shirt to any lens I care about. The fibers are rough enough to cause micro scratches, but more importantly, the cotton fibers are not able to lift and hold dust so you drag the dust around on the lens. if there was a piece of wood dust or sand, you could be scratching the coatings by cleaning.

I prefer to blow off large particles with the rocket, then very lightly brush the element with a lens pen brush. And only then if there are water spots, fingerprints, grease, etc, that remain, i use the lens pen tip. In the absence of a lens pen, i would use a microfiber cloth.
Make sure your cloth was not washed using fabric softener or it can leave a residue that is hard to remove.

Let's be careful out there!

[Anvh]

LensRentals.com - Front Element Scratches

About the wash softner, never use it actually.
It will damage the absorbent nature of towels, cloths and make clothing less breathable.

ps. wood is not harder then the lens coating so it won't leave a scratch, sand probably will though.

[Deimos]

Thanks for the input guys, I will see if I can get it cleaned. Ill let you know what happens

[Deimos]

Would it possible to post a photo of the mark?

Gee whiz my brain, I said I only had one camera....BUT I have about five lenses Just realized I could switch the sigma off my camera and take a photo using another lens DUH.....

Ahem, here are a few shots that give an idea what it looks like. It was VERY difficult to get a shot of. I tried to clean it again with some moist breath and a cleaning wipe no change at all. I will take it to the camera store this weekend and have someone else take a look and see about a product to try to clean it. That said I think it is cleaning damage. It forms an even circle roughly but it was impossible to show in a shot

[altopiet]

Gee whiz my brain, I said I only had one camera....BUT I have about five lenses Just realized I could switch the sigma off my camera and take a photo using another lens DUH.....

I thought of pointing that out, but figured you'll realize it in the end

Are you sure it is not haze due to lens separation, but actually on the outside of the lens? Either way it might be better to return it, as it do not seem like something that normal cleaning will remove.

[Wheatfield]

If that is on the outer surface, it's cleaning damage, and the lens is effectively valueless junk.

[Deimos]

Thanks guys, I have contacted the seller about a return. We will see how that goes...