It looks like some kind of hand-applied finish with varying tones. Try Winchester Tiles: https://www.winchestertiles.com/

Thank you! I had a designer tell me they think it’s clear glass tiles?

Clear glass would be much more translucent than that. There are a few colored glass tiles that might qualify like the melted glass I am listing below. You are seeing a gloss topcoat with some sort of variegated finish underneath which is typical of hand-painted, ceramic tiles. There are a few other companies you might try:

• Australian for Mosaics, Tundra Melted Glass Series by http://www.maniscalcostone.com/
• Pratt & Larson handmade ceramic tile
• Triton Stone - this is a dealer that has tile similar to the look above, but I have only photos saved on my phone and not the brand names of those tiles, so if you have a location nearby, you might stop in personally

To be honest, for that exact look you're seeking, Winchester or Pratt & Larson have that look perfected. I know both those companies are expensive, but for a backsplash area, perhaps this would be a splurge?

This last photo is the Tundra Melted Glass. Above photos are combination of Pratt & Larson and Winchester. Click on each photo to expand and see all the color options.

The kitchen is by Stephanie Gamble Interiors - she describes them has handmade grey tiles bought at Chesapeake Tile and Marble (no brand info). Here’s a different view - the grey is much more noticeable

Try California Art Tile (manufacturer),

Suprema (tile name), "Carrara Gray" (color)

https://www.mexicanhandcraftedtile.com/all-products

These are all beautiful! I can’t wait to look into them all!

California Art Tile's Suprema also comes in "Touch of Gray" and "NY White," if "Carrara Gray" doesn't turn out to be the exact right shade. If ordering samples, ask for all 3 of those colors.

I have Suprema "Ice Blue" as my backsplash and I LOVE IT! California Art Tile's handmade tile is gorgeous.