Handmade solid yellow bronze also called jeweler gold bronze small sea urchin necklace with embedded midnight blue sapphire. This urchin is called a Tuxedo sea urchin. There exist 950 different type of sea urchin.
 
I made my own mold from an actual urchin. Each charm is individually made and signed in the back. 
 
2 mm sapphire embedded in its center.
The charm is about 15mm.
 
The shown satellite chain is very dainty and is not recommended for longer than 18" long. 
Other 14k gold filled chain length and thickness options are available.
The thin chain is 1.4mm.
Gold filled has 100 times more gold than plated thus does not rub or peel off.