It's your rag, or what you are using to clean them. The counter is inert and cannot absorb anything that would lead to it having an oder. Throw out your rags and buy new microfiber. Then clean the counters well with a good detergent, like Dawn. Wipe again to rinse with a damp microfiber. Dry with a microfiber.

I clean mine with Method cleaner and paper towels. To be honest, I don't have the patience to rinse soapy water off counters.

"Dish rag is clean".

Yeah, I believe her.

Silestone advertises: "Silestone® is the only countertop with built-in Microban® antimicrobial product protection to safely fight the growth of odor-causing bacteria 24/7 for the life of the product. As a result, Silestone® is easier to clean and stays cleaner in between cleanings."

So it is unlikely that it is the Silestone itself causing the odor. Either it is as Sophie says - that the rag is not as clean as the OP thinks it is - or, there is something funky with the cleanser the OP is using, OR…it is not the Silstone counters causing the odor, but something nearby, like some garbage caught behind a drawer, or old food caught in the underside of the counter's overhang and when the counter gets wet, water drips there and it smells, or the DW has some food caught in the filter or drain and smells funky, or the sink's drain is not vented properly and wafts an odor, or there's a sponge nearby that needs to be replaced, or the hood filters haven't been cleaned - any one of these, or other culprits, could make the OP think it's the counter that is smelling.

Hmmm...on another forum a guy was not going to buy a particular front load washing machine because he could not stand the smell of the front gasket which was reportedly impregnated with microban.... Maybe only some people are sensitive to the smell?

Have the counters always smelt, or is this a new problem?

Do you have a lot of seams? Is there grout rather than epoxy? There's a thread right now on the Bathrooms forum (here, towards the end) discussing the possibility of grout smells in reaction to water.

Sophie is right. The counter material is inert -- like the glass in your windows. The Method (purple liquid, forgot scent) is nice and doesn't streak. Use a paper towel or as has been suggested a clean microfiber. Mrs. Meyer's lavender spray is also very nice. Both leave you with a clean counter or stove or sink area and a smile on your face.

As to those front loading washers, I think that they are handsome looking, but they certainly have known stinky issues. They also seem to have an issue with the bearing (horizontal shaft) wearing out. I'd love to have a dollar for ever curb alert CL ad I've seen for these broken, fairly new, front loading washing machines.

Our family had a front loader way back in the 60's. Maybe it was a Bendix (?). I loved to watch the clothes get tossed around and then spin. With that one, there was absolutely no friendly way to add a forgotten item once the machine was filled.

We had a used ($100 with guarantee) harvest gold (ugh, but in cellar) Whirlpool HD for 30 years (minor repair, like lint filter that we tossed). A few years ago, we got another simple, non-computerized H D Whirlpool or simple thing, only a few features, but fit in the SUV and it was only $100 nearly new via CL. Works fine. It's in the cellar, next to the 35 yo used Maytag non computer, avocado green dryer. When it's nice out, I actually like to line dry.

A dead mouse?

Edit: I am serious, a dead creature.

What do you wash the cloths in? Some have had issues with downy fabric softener causing smells in clothes. Take a clean cloth and smell it, get it wet and smell it again.

I use microfiber cloths (just started using Norwex) use a tiny amount of detergent to wash them and rinse with vinegar. No dryer sheets!

What product are you using? I have started using only water with Norwex cloths on my granite.

I am not endorsing Norwex just mentioning as Norwex cloths are very different from other microfiber cloths and I found plain water works great with them. With other cloths I used to use all surface Pledge.