Ores
crossroads:gem_ruby
Crossroads adds a few ores to world gen. Crossroads also adds several methods for <thing><link:rotary/millstone>ore doubling/$ and a method of <thing><link:rotary/stamp>ore tripling/$.

<item>Copper/$ is quite common, spawning in large veins below y=30.

<item>Tin/$ is about as rare as gold, spawning scattered as a single ore block below y=30. For an optional extra challenge, you can keep Crossroads tin separate from other mods' tin, and use only the Crossroads tin for Crossroads machines.

<item>Ruby ore/$ only spawns in the nether in veins of nether quartz ore. It is overall quite rare- but easy to find if you mine quartz ore veins. It drops <item>ruby/$ gems, which are used for <thing><link:intro/beam>beams/$.

<item>Void ore/$ only spawns in the end on the outer end islands. It fairly easy to find. It drops <item>void crystals/$, which are used for late game <thing><link:intro/beam>beams/$ (specifically creating <thing><link:beam/void>void/$).