The turquoise cross is set in gold and could be as early as 1820 although at this date it would have been on a ribbon not a gold chain ,which will have been added at a later date.
It is not easy to find something on the internet about this cross.
What did we find .
From the goldstamps there is perhaps more to tell.
The stone could be turquoise or lapis lazuli.
It is hard to tell where and what time it is from.
Regarding the brooch it could be from a `the grand tour `as well .
At 1870 you see " look a like crosses " inlaid with pearls or coral.
It could well be 1820 where again "look a like " crosses are found in Belgium and the south of the Netherlands.
But please tell us if you know more and help us solve this puzzle as well .