All of the armor types
1. Emerald
2. Ruby
3. Sapphire
4. Amethyst
5. Topaz
6. Onyx
7. Tourmaline
8. Garnet
9. Jade
10. Pearl
every one of these armor sets is better than diamond and you'll find the all of the ores under y=20,
You can also make blocks out of these minerals that can work as beacon bases