Any true Vanderbilt jewel diamond ring dated 1960 would be considered relatively expensive. The best place to find this ring would be at an auction house.
The Vanderbilts' are "old money". They were wearing diamonds back in 1910 and Large diamonds at that. Any piece of diamond that was genuinely owned by the them should be classified as an antique and quite expensive. If you were planning to buy one, an auction house like Christies will be your best bet.
Quite possibly, yes. The Vanderbilt family probably owned diamonds and probably had them set in engagement rings in the 1920s. Sight unseen, and without a paper trail -- provenance -- it is impossible to determine whether a diamond is a Vanderbilt Diamond or not, regardless of the age of the ring.
Stone for stone, a diamond is more expensive than an emerald.
The most expensive diamond, by definition, is priceless.
Platinum is not more expensive than a beautiful, natural diamond.
Red diamonds - are the rarest and most expensive.
By weight, when comparing equal amounts of platinum and diamond, gem-quality diamond will always be more expensive.
All else being equal: carat weight, cut, and clarity, a blue diamond will always be more expensive than a white diamond.
No, the Hope Diamond is not the most expensive diamond in the world. While it is one of the most famous and valuable diamonds, there are other diamonds that are more expensive due to their size, clarity, and color.
Both are considered expensive, but a diamond is more expensive simply because it's a harder mineral.
All else being equal: carat weight, cut, and clarity, a red diamond will always be more expensive than a white diamond.