Crystal is stronger than standard glass which is why it can be so thin.
Modern production of lead-free crystal is generally pretty good now. Old leaded crystal is extremely brittle and prone to chipping and fractures which definitely soured people's perception of its durability. Our glassware uses titanium as a strengthening additive which really helps durability as well as sparkle.
Most of our hospitality partners use them in service every day in commercial dishwashers with very little breakage. Having a shorter stem also greatly reduces both tipping and twisting scenarios which are the most common sources of breakage.
Crystal consists of many raw materials with silicon dioxide making up the majority of the mix (70+%). Titanium dioxide is melted in with everything in a brand-new solar powdered furnace that runs up 3,000 degrees Fahrenheit iirc.
Titanium has the highest strength-to-weight ratio of any metal which is why it's used in the most demanding applications like rockets.
Each glass manufacturer uses their own recipe and pretty much all of them use aluminum, rather than titanium, as their strengthening additive simply because it's exponentially cheaper.
Glass is normally made with 50-75% silicon dioxide (sand, basically) and the remainder various metallic salts or oxides like lead oxide, soda, potash, etc. These are combined as powders and when you melt them down they all dissolve together into glass.
From a layman's perspective all these metallic compounds seem really different from glass but in reality that's the magic of glass. I'm no chemist but SiO2 doesn't seem chemically very different from PbO or TiO2.
