[Paul R.]

Ah, I looked it up on Wikipedia, and, a bit to my surprise, the planet's makeup* has nothing to do with it: A superEarth is apparently defined by being "an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively.

Even "substantially lower" (mass) is a bit of a loose constraint, I guess: 12.9x Earth vs. 14.5x does not seem a whole lot lower than Uranus, tho' we're getting there with Neptune (17x), I suppose. I propose 10x to 14x as "Super Duper Earths". Heheh. *Looking into this, I was reminded how cold Uranus atmosphere is, as low as -225 deg. C and 560 mph winds. Yikes!

[SunkenCiv]

Figuring out the composition remains (mostly) beyond current technology; about the only things that can be estimated are size (brightness and sometimes diameter) and with a system of this kind, the mass of the bodies (including the star) can be ballparked, and then slowly refined. And you're right about the definition, there appear to be as many defs of "Super-Earths" as there are astronomers. :^) Smaller than Neptune and Uranus (which are not the same size anyway) isn't much of a constraint. :^)