Alpha makes outstanding diamond tools for the stone industry. They can also educate you on the science of diamond tool technology
You have to choose the correct bits and blades for the stone you're working. You can simplify it by selecting equipment for granite, then everything else.
Granite blades/bits have a softer steel core the diamonds are sintered to. This is so the steel wears away exposing fresh diamond constantly. Softer stones should be cut/drilled with a harder steel core blade to prevent the metal from overglazing the diamonds and effectively killing the ability to cut those stones. If your blades wear out quickly, or cutting performance decreases quickly - you're using the wrong blade or bit type for the material you're working.
Coolant depends on blade design. Continuious rim blades tend to require coolant, segmented blades are usually wet or dry use. High rpm blades are dished and segmented so the steel core can deform under high RPM and heat into a flat blade... so if you're wondering why some blades look cupped, that's why.
Lots more could be said on the subject of diamond tools and diamond tool technology, but I point you to Alpha for more info. They make some first rate tools.
I've worked in stone professionally for over 18 years, fabricating for money, sculpting for fun.
