Tungsten is a natural element which has many unique properties. It has the highest melting point of all non-alloyed metals and is extremely hard - approximately four times harder than Titanium. Tungsten is most well known for its virtually scratchproof qualities. Even in high impact environments, tungsten will not scratch.
The product you have purchased from Weta is a Gold Plated product - with reasonable wear and tear the gold finish should retain its lustre for at least 2 years.
Tungsten carbide is 100% hypoallergenic and will not produce skin irritation or discoloration. Tungsten does not react to sunlight, salt water, chlorine or anything that the body emits.
Tungsten carbide rings require other metals to be used as a binder, in the case of the One Ring, nickel is used. Tungsten bonds to the nickel molecules, preventing them from leeching into the skin. This is why Tungsten is hypoallergenic.