How can I understand if the brush I bought has natural or synthetic bristles?

[StellaStellitsa]

I bought a brush today. I asked for a natural bristle brush. Now that I'm home I think it may have synthetic bristles instead of natural. Or maybe a mix of the two. How do I distinguish them? I can see irregular thickness and length, mostly black coloured but some are lighter, reddish brown and white.

Edit.
How is a natural bristle bush supposed to leave my hair feeling like?

[Sarahlabyrinth]

Pull out a bristle and burn it, it will either burn like plastic or hair.

[StellaStellitsa]

Pull out a bristle and burn it, it will either burn like plastic or hair.

I tried it. It burned like hair. I am happy for it. Thank you for telling me.

I now think it may be a mix. I now may need to burn a thick one.

[StellaStellitsa]

The thick ones burn like plastic. So, it is a mixture of the two. Mystery solved.

Now, how are they supposed to leave my hair feeling like?

[lapushka]

Did you perhaps buy a mixed BB? Mixed boar bristle brush, with nylon hairs stuck in? They usually stand out right in the middle of a "bundle" of hairs.

Not everyone benefits from a BBB or mixed BB. You'll have to see how you fare. I have wavy hair and never got along with BB; it will kill your entire wave pattern and fuzzle it to bits.