Copper... or bronze?

Arcadius from around year 400:



anonymous folles in the 1000s:




Just a question I want to be 100% sure and not 90% sure:

COMMON Byzantine coins from Arcadius(400s) until Alexios I Komnenos (around 1100) are made of what exactly?

only copper?... (which is fragile)

or bronze? (90% copper and 10% tin which is very hard).

I hope one here knows.

Thanks

 

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https://www.conservationphysics.org/ppubs/byzcoins.pdf

 

So both copper and bronze are used.

 

I always thought it was copper. At least the unpatinated portions of a coin are reddish in color.

But according to the paper, most coins from the western mints are bronze, and eastern mints are copper.