When rappers refer to their "ice" they are refering to diamonds, and diamond coated jewelry. Black people like ridiculously expensive gold and diamond jewelry. Black people also like crack, not meth.
However, ravers do like meth! So if you hear a raver talking about their "ice" they are probably refering to high quality meth, which appears as clear shards or chunks, hence the name "ice."
There are some purists here who will say after me that true "ice" is actually 4-methylaminorex and not meth. I say, fuck these people. Because there is basically no 4-methylaminorex on the street due to whats involved in producing it. Meth is simply easier to make and still keeps y'all ravers tweeked for days on end. These same purists will probably tell you that "ecstacy" means only MDMA. That is also bullshit, I know of at least 20 different drugs that are sold on the street in pill form as "ecstacy" with mostly positive customer feed back.