To be honest, this is a very vague question to be able to provide even a remotely close answer but here are my observations. At first i thought it looked like some aluminum alloy but it definitely does not match your weight and volume measurements (assuming a thickness of around 0.5cm). It is at least 3 times heavier than AL but that narrows it down to hundreds of possibilities (only in the metal and alloys family). The simplest way is to ask the guys working at the shop, they might be able to tell you. But if you are really curious about it and wanna go deeper you can try a scientific approach:
a) You could probably assume it is a metal, although there are way too many engineered/composite materials in the market as well
b) Use physical data as much as you can (density, hardness for example since you already have these). Use known materials and see which ones it can scratch and which ones can scratch it.
c) Check whether it is a magnetic material, there is also a spark test for metals, look it up
But even with this approach you might still end up with dozens of possibilities.
If you really have to know and are willing to invest money in it you can request a PMI or OES test from a local lab, they are readily available and the test takes only seconds to provide a detailed description of the chemical composition of the sample.