I thought I was Professor Cardamom, really. I had my my white, my green, my black; everything was in its place, and I had all of the facts lined right up.
But these days I know I have no answers.
I was wandering around Asia Market Corp. in Chinatown impulse-buying star anise and really weird-looking cinnamon when I noticed something I hadn't seen before, tsao-ko. Tsao-ko is apparently another transliteration of cao guo (草果, I think), a.k.a. black cardamom. Black cardamom has practically nothing in common culinarily with the green cardamom you're probably familiar with - where the green is a nice little spice, goes well with sweet things and baked goods, black cardamom is harsh and wrinkly and smells like a medicinal campfire. Great for stews, though!
The thing was, this didn't look like any black cardamom I'd ever seen! I'd always bought it from Indian grocers, nice wrinkly smoky little packages, whereas this stuff is huge, much smoother, and basically just plain terrifying. Picturewise, Chinese is on the left, Indian is on the right. I don't even know if that image does it just, even.
Breaking them open, they smell and look pretty similar, except the meat instead of Chinese kind seems a little more dry, and there's a little less extra airspace in the Indian ones. Plenty interchangeable, I'm sure, with the exception that it'd take about 5 of the Indian kind to match up with the Chinese ones.