The malachite piece looks like it was made by a hobbyist/student.Excess solder in a number of places and poor bezel setting.
I believe some time in the 1970's a woman was making synthetic emeralds which had natural looking inclusions.The original samples she sent to GIA...
The cut of the stone doesn't look unusual,looks like thousands of others cut in India,Ceylon,etc. They were cut for weight and not regular facet...
The top buckle may be petrified wood and the cats eye is tiger eye quartz.
Hard to tell what casting process was used and if the texture was from casting or applied on the second one [MEDIA]
Looks like a zodiac ring.
It's where there was a gold star.
Photo too blurry to tell what the edge border is,the left and right panels are wriggle engraved. Size of the plate might help.
It looks like a Chinese fake.
There are various acids and other techniques to remove lead/tin solder from gold,I have never needed to try them out........
Depending what type of solder is on it,a little nitric acid may clean it up.
750 would refer to the appropriate gold content of any color gold.
Most Madeira citrine is heat treated amethyst.
Pieces from a single mine can look different,see link https://waddellgallery.com/pages/turquoise-materials
Looks a bit like a fossil bison tooth..... https://www.paleojoe.com/product/fossil-bison-tooth/
Looks like many were inlaid with silver wire.......
Looks like it is soldered granulation,too many areas are flooded with solder.
The tufa stone molds are only good for 2 cast if your lucky,most likely they were sand cast. https://www.shopgarlands.com/blogs/news/tufa-cast-jewelry
Looks nothing like a sharks tooth.
The photo is too small to see anything.
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