According to my view, granite is better than slate because slate can scratch easily and make them less visible where as granite will not scratch easily and can be cleaned with a mild soap and water..
So, it is better to use granite.....

Thanks for the input! This is my first time to "build" and making all the decisions is hard!
I think we are going with river bourdeaux granite. The perimeter cabinets will be painted a creamish color (yet to be determined) and the island will be a stained dark. Floors not yet selected.

Here is a picture of river bordeaux granite:
https://www.houzz.com/photos/river-bordeaux-granite-counter-tops-traditional-kitchen-albuquerque-phvw-vp~8835934-Bordeaux-Granite-Counter-Tops-traditional-kitchen-albuquerque

The honed granite sink I'm considering (the dark one)
https://www.stoneforest.com/kitchen-bath/products/view/120

And a slate sink:
https://www.houzz.com/photos/custom-kitchen-in-libertyville-farmhouse-kitchen-chicago-phvw-vp~695389-1-Custom-Kitchen-traditional-kitchen-chicago

Either one, I will have to order w/out first seeing it. Sheldon slate is sending me sample slates, though, to choose from.

Thanks for your advice! =)

It may be easier with pictures rather than links. Here's a picture of river bordeaux granite.

Here's a picture of the honed granite sink. (It's the dark one in the middle).

And here's a slate sink. (Sorry for the multiple pictures. I couldn't figure out how to put multiple pictures in one post).

And another...

I'm not sure about slate but wouldn't the granite sink become a bacteria breeding ground?

Make sure whatever sink you select has IAPMO approval or that such approval is required by your building inspector before issuance of a certificate of occupancy.

These sinks aren't cheap and probably not refundable. The last thing you want to see on it is a red tag.

How thick are your countertops going to be? The standard slate slab (and therefore sink) width is thinner than those granite sinks you show, and thinner than the average granite counter slab -- will the difference in edge width bother you along the exposed front of the sink?

I suspect either would work just fine. For what it's worth, there's a very long history of slate sinks, but not so much with granite, so with slate you'd be getting something time-tested.

I'm not sure about the bacteria breeding ground, Quadesl. Is that true of granite? Good point, Trebruchet. I'm not sure about the IAPMO approval. I'm not sure how that process works. I'll have to check into it. Thanks, circuspeanut. I hadn't even thought about that. The slate sink is 1" thick. The granite sink is 1 1/2" thick. I think our granite counter tops will only be 2cm thick. But then I guess the front "edge" of granite countertops is usually thicker. Hmm...
circuspeanut, if your slate countertops are 100 years old, then slate must be very durable! Is the maintenance easy? Do you have to seal it periodically, and if so, how often?
Thanks so much for the input!

I absolutely love that granite, but I'm not sure about the granite OR slate. It looks like they're both introducing a new color that's not repeated in the counter. How do those sinks fit with the rest of your color scheme?

Slate is simple: soap and water, no sealing required. Mind you, our slate is from 1910, so I have no experience with "younger" slate.

If you go for slate, Sheldon Slate will tell you everything you need to know, they're fabulous to deal with.

Why would a granite sink be a bacteria breeding ground? Assuming that it's nonporous, which many granites are, bacteria shouldn't be a problem.

chiefy76- well we don't actually have a color scheme yet. The granite is all we have selected. (The picture of the granite is not my kitchen, just a picture I found with a good view of the same granite I have chosen). Thanks, circuspeanut. I have spent a lot of time on the phone with John at Sheldon Slate (he's probably tired of my questions. lol). He is sending me samples of the slates and has been very helpful! So hopefully one of those samples will look great with the granite and it will be an easy choice, because I have decided I really want the slate!). gladys1924, I wondered the same thing. Thanks!

This company offers many maintenance free farmhouse sinks. Might be worth a look!

Here is a link that might be useful: World CopperSmith

What did you decide on ?

atrapnell, I am totally obsessed with the look of the honed basalt granite farmhouse sink from Stone Forest! there is a floor model nearby that is being sold at a super discount and I'm really contemplating purchasing it but I cant find any reviews on the maintenance from an actual user of the sink or any honed granite sink for that matter. What did you end up going with?

I am a geologist and I don’t think real granite is a good sink material. Unless there is a new product I don’t know about, it is my understanding your granite sink cannot be sealed to remain impervious to water. Without a permanent sealer, water will erode your granite sink - some water faster than other water. I am not someone who worries a lot about bacteria, but all the little cracks, nooks and crannies in the not imperviously sealed rock will provide a home for bacteria too. Unless you don’t use it, it is going to have water flowing over it and sitting in it a lot. I wouldn’t do even a fine grained, uniform granite as a sink.

Granite constantly exposed to water.