-Aluminum oxide - This is the most common material/crystal used for microdermabrasion because it is non-reactive and highly effective in deep exfoliation. 

-Sodium bicarbonate - This material is softer and gentler and is often the material selected for when someone has sensitive skin. It is used for lighter exfoliation but it still effective for resurfacing the skin.

-Magnesium Oxide - This material is similar to aluminum oxide but it sometimes selected for its different abrasive properties. 

I like how you broke down the three different types of crystals and explained what each one is used for. I didn’t realize that aluminum oxide was the most common one because it’s non-reactive, but that makes sense why it would be used for deeper exfoliation. It’s also interesting how sodium bicarbonate is a gentler option, especially for sensitive skin, because not everyone can handle more aggressive treatments. The part about magnesium oxide being similar but chosen for different abrasive properties was also helpful to understand. Overall, this really shows how important it is to choose the right type of crystal based on the client’s skin and what results you’re trying to achieve.