An engagement ring can be anything you want it to be. The DeBeers diamond company really got the diamond engagement ring tradition going because they wanted to sell more diamonds.
Blue Diamond
Sapphire
It is a myth that a lost stone from an engagement ring is bad luck. Engagement rings or any ring a person wears often should have the claws checked by a reputable jeweler once a year and it is not very expensive to do so.
No, it doesn't. Make it what you want it to be.
Sapphire
A solitaire engagement ring is one that features a large center stone. Traditionally, the feature stone is a diamond. The engagement ring may, however, include any type of gemstone. Strictly speaking, the solitaire ring is a one-stone style. You may find, however, that any ring with a large stone and smaller, accent stones may be called a solitaire. One example of this variation is the halo ring, which is a center stone surrounded by small diamonds or other gems.
- size of the band - color, cut of the stone - price
If someone needs an engagement ring sized or resized then most good jewelry shops will have someone on the premises who can do it. It does not matter about the size of the stone.
Engagement rings are traditionally diamond so this would be the best stone to have set in a white gold ring for this purpose. If you would like to be less traditional then you could use ruby, diamond or sapphire, either alone or alongside diamond.
396
Yes, tanzanite might be a semi precious stone but ultimately it is up to the wearer/bride as this is a very personal decision.
You can use any ring for either one. Usually an engagement ring has a main diamond and maybe small ones around it or just one stone. I had a carved jade ring for mine. An anniversary ring is often a bigger stone you can afford now that you're settled down with a job and a house to rededicate yourself as a couple. It can be any style you want. There is no custom that people in general follow for this type of thing.