Gems, jewels and runes cannot be directly equipped. They are used in equipment embedded with grooves to increase the properties of the equipment. As for gems, three broken stones can be combined into 1 cracked stone, three cracked stones can be combined into 1 ordinary stone, and so on. The higher the level, the greater the role of course.
All kinds of "broken" gems have a special function in 1.09 and previous versions, that is, synthetic blue equipment. This function was cancelled in later versions.
It seems that you are new to Diablo II, and you don't know these basic knowledge. In fact, according to my experience of playing the stand-alone version many times (of course, I have also been to many domestic Diablo II Battle.net), all kinds of "broken" gems picked up at the beginning of the game are actually of little use, except sapphire, which has some freezing effects, and other gems can be sold directly. When you need high-grade gems in the future, your character level and monster level will be higher, and monsters will directly drop high-grade gems.