Can this be regarded as a tartan?

[JakobT]

It's a tartan, it's just not woven in the twill pattern.

Yes, 9 cm is a bit small for a kilt tartan, but you can go ahead and make it anyway, right? I'd pleat double setts, too.

Looks like twill to me. It has the diagonal twill lines.

[Carolina Kiltman]

Looks like twill to me. It has the diagonal twill lines.

Unless my memory is faulty (not unlikely!) or the definition of twill has changed, (quite possible) a twill weave is two threads of weft crossing over and under two threads of warp. That is what gives it that distinct diagonal line. So I will second Jakob here. Looks like twill to me too.