This is just slightly thicker than the average kitchen countertop. Most of our steps are pool coppings are 5cm, or about 2". This thickness sounds average, and I don't think that it will look cheap, but it is your house and your taste is important! Make sure that, if you want thicker, it is actually available in your area. Your installer may be recommending this thickness because it is readily available.

I would suggest 3 to 3.5 inch thickness. Of course,it will be more expensive. But if you were using a brick tread the thickness would be around three inches if it was laid on it's side. But the dollars always play a big role in these decisions.

Thanks to both of you for your suggestions. I will talk to the mason and find out if 2" would make much difference in how it looks and how much it costs. I see on the Internet that many stone "warehouses" stock 2" min for bluestone stair treads.

I just put in a new Bluestone and brick walkway. I also used bluestone for tread. Mine is 2.25 inches thick and looks nice and substantial I think. It leads up to a new portico still under construction. I tried to attach picture but it's not working. You can look at them when you click my picture. They are under my project called Bluestone Walkway. There is one with my dog on it that's up closer so you can see the thickness.

Your new walkway is beautiful. I love the style of your home, too.
The mason says it would need to be special ordered to get the depth we need - 14", at a thickness of 2". Because it is heavier to work with, they don't keep supplies at the warehouse. Bummer - I hate to do this renovation project (it was necessary as the brick steps were loose and coming apart) and end up with something that looks less substantial. The good news is all the homes in the neighborhood are similar, with the brick front steps - a tread of 1.5" thick bluestone won't look bad, I guess I had hoped to spend all this money and get something I thought was quite a bit of an improvement.
Thank you for your response and photos.

My step is 16" deep, and it took less than a week to order. I needed 2 pieces because it is 11 ft wide. Stone is very expensive I agree. Due to the way our house is angled on our site walkway was over 650 sq ft because it's so long. I could have done a stone patio with it being so long, but finally had to do it. Waiting each year wasn't getting any cheaper:( anyways it's fun to talk with people that like design. Not too many people I know do.

Yes, I agree it's fun to talk to people who like design - everyone on here will get my need for aesthetics. The mason, however, was probably not expecting me to be so detail-oriented. My steps are a bit over 8-feet wide so he cannot use the 8-foot standard length. It would look nice to not have a seam but when he explained how he will cut it, I am not too concerned about it. It seems so nit-picky to ask him to special order a thicker size when he was excited to complete the job by tomorrow - however, it is costing thousands of dollars so I feel it is somewhat justified. Enjoy that new walk and portico of yours!

Our local stone yard keeps bluestone in a 1 7/8" thick to 2 1/4" thick. We use them for fireplace hearths and I don't think the thinnest pieces look skimpy at all, and they're only 3/8" thicker than what you are talking about.

I don't think a 1 1/2" piece will look bad. I understand what Walsh Krowka is saying . . .a brick rowlock would be about 3 1/2" - 4" tall, but that's not really a design necessity, that's just the nature of the material.

I think part of the real issue is trying to get your step treads and risers to look right without too much brick cutting. If you're using normal modular brick, two visible courses of brick are about 5 1/2" tall, plus the 1 1/2" slab of bluestone, giving you an ideal step of 7" tall. Jumbo or Queen sized brick or thicker treads will make your steps too tall.