saltillo tile question

We have saltillo tile throughout the house. I've tried lots of products to try to get it to shine, but nothing I've applied seems to shine for very long. Is there some secret to this? I've seen shiny saltillo floors in banks, restaurants and other public buildings. They almost look like they've been varnished. But when I ask how it's done at these facilities, no one seems to know. Any ideas out there? We've resealed them already, but they still won't hold a shine.
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