Take your stone to a gemologist, who will ascertain its cut, colour, carat weight and clarity.
Then take these details to a jeweler, and ask how much s/he would want for a stone of that quality.
The price depends on two things: the karat value of the white gold and the colour, cut, clarity and carat weight of the stone.
Halo moles.
The value of a diamond depends on its cut, its clarity, its colour and its carat weight. A local jeweler can give you the answer you want.
You need to find out what type of diamond and what type of setting your girlfriend likes. Once you get that information you should go to a jewelry retailer and they will help you in your decision. I would recommed a white gold setting with a diamond that is on karat or larger Listen to your girlfriend and take notice of what kind of jewelery she likes. Look at the color of her jewelery (white gold or yellow gold) and also take note of the shape of stone she prefers (princess cut, round cut, etc.)
The 10k identifies the metal as 10 karat white or yellow gold. Ud is probably the jewelers mark such as Ultra Diamond.
Probably 18 karat gold/nickel alloy. White gold is gold mixed with nickel and looks silver.
10K white gold will turn yellow
10 karat W likely refers to a piece of jewelry that is made of 10 karat white gold. White gold is a popular choice for jewelry and is made by mixing gold with other white metals like nickel, silver, or palladium to give it a silver color. The karat measurement indicates the purity of the gold, with 10 karat gold being 41.7% pure gold.
22 kgp means 22 karat gold or 22 karat white gold plated
The hallmark 375 on a white ring typically indicates that the ring is made of 9 karat gold. The CZ likely stands for cubic zirconia, which is a synthetic gemstone used as a diamond alternative in jewelry.
The stamp SB14K on a white gold diamond band ring indicates that the ring is made of solid 14 karat white gold. The SB stamp typically refers to the manufacturer or the brand of the jewelry piece, but its specific meaning can vary depending on the jeweler.
Every diamond is valued by its cut, colour, clarity and carat weight. Also, please note that pure gold is only 24 karat. Take your jewelry to a certified gemologist, who can help you identify these characteristics in the jewelry components, and also help you establish a value for this piece.