Hi Memries,
I have gotten to know a very knowledgable and sincere couple who do the expo circuit here in my area. They sell crystals of all kinds, and they also sell dichro, and jewelry. They are really special people, and the husband of this dynamic duo gave me a little lesson in checking to see if a crystal face has been tampered with or not.
I was showing Brad my lemurian seed crystal and he noticed that one face of the point had been polished. I was pretty shocked. I had payed pretty good money for it at a store I trusted. And my friend explained that only the one face of the terminal point had been polished, and that probably it had been chipped and so someone took it upon themselves to "fix" it. I don't think that it takes away from the crystal at all. All of the other faces are natural.
What I learned was that if you tip the crystal this way and that in the light you will see little imperfections and marks in the surface of the crystal. Polished crystals won't have that. Look closely at the surface of a crystal that you are pretty sure hasn't been polished. Then look at a polished surface. You'll see the difference.
Also, if the grooves are faked, that is also something you can see pretty immediately on close inspection. And, not many people want to spend the kind of time it would to take to cut the grooves in the crystal. You won't get the right effect anway. My personal opinion on that last bit.