This is an old Victorian mourning pin with onyx (tested), opal (not sure real or not) and seed pearls (real).

I have tested the pin throughout as there are different colors in the metals.

The gold color back and the cube on the stick pin are 14K.

The stick pin (pin portion), chain and silver color on the back side of the pin are not gold (or less than 10K gold as my test kit does not test below 10K).

There is no marking on it.

The circle pin measures 1-1/8 inches in diameter and 5/8 inch thick.

There are only 4 groves on the round dome onyx at 2 / 5 / 8 / 10 o'clock positions. Somehow the pictures have lots of reflections.

The cube on the stick pin is about 3.5 mm all sides.

The entire pin weighs 12.5 grams.

Condition is previously owned and there are some chips on the onyx edge but hard to see when wearing! Otherwise, they are in fairly good condition considering its age. 

I have acquired it from an estate sale in Laguna Woods, CA and I have no other information or history about it.

A dime is placed for size reference and not included.

Shipping includes the necessary insurance and everything has gone way up in price!