Thoughts on this portrait please- date of jewellery?

I searched for 'Castellani Etruscan revival earrings', but the style is more broadly known as 'archeological revival'. The Castellanis & Carlo Giuliano, who was with them before setting up on his own, are the famous names, but the style was widely copied.

https://en.wikipedia.org/wiki/Fortunato_Pio_Castellani

https://en.wikipedia.org/wiki/Carlo_Giuliano

Pieces from their workshops command big bucks today.

 

And a bit of beauty advice as well.

 

Could her necklace possibly be a mirror pendant?

 

It's so improbable looking, it's possibly anything.

 

That technique was popular over a long period of time, from about the 1850s to the 1930s. It was invented in the 1850s. Here is some information. Besides solar enlargements, other names by which they were known were crayon portraits and crayon enlargements (although crayon was not always the material used for going over the photos).

http://sgarwood.com/node/52

This one is a pdf file, an article that goes over the history and some technical aspects: http://resources.conservation-us.org/pmgtopics/1989-volume-three/03_05_Albright.pdf