Was sure you would like this, Helen. I enjoyed your posts on colour, but read them too late to contribute. I do have a couple of comments on your queries.

Minium and Cinnabar are two different chemical compounds. Minium is Red Lead or Lead oxide and is made by heating White lead, which in turn, is the whitre substance that collects on lead shavings when immersed in vinegar. This is not a mineral.
Cinnabar is Mercuric sulphide. This is a mineral and the Almaden mines in Spain are famed for this.

but if you have a link between cinnibar( arabic for mercuric oxide) and minimun
I don't know from which eaxt period, minium was used as a pigment, but, Almaden Cinnabar has been mined even in the classical world.
Though separate compounds, the Almaden ore has been called both, Cinnabar and Minium. The former, as you pointed out, has the Arab (from the Persian) root, probably contributed by the medieval occupation of Spain by the Arabs. There is a Basque word for Cinnabar, arminea(there is an accent there somewhere), and the Latin, minium, might have this as a root.

Coming back to miniatures, such paintings date from ad 3rd/4th century, and were then called 'historia'. The Elizabethans called them, 'limnings'. The red pigment minium that was used for both the paintings and the text in what were then called, 'illuminated manuscripts', and an etymological confusion with 'minute', resulted in small sized paintings being termed, miniatures!

I got a lot of information on the fascinating subject of colour, from a book by Victoria Finlay. I have read a couple of other books on the subject that are somewhat more detailed, but this one is not as pedantic and is also a bit like a travelogue.