I would use Unakite Jasper:
For lasting love, Unakite is traditionally sprinkled with dried yarrow and placed in a sealed bag as a marriage or commitment symbol. It should be replaced on anniversaries and the old crystal and yarrow cast into running water.
Unakite Jasper fosters healthy relationships through balanced emotions. It encourages harmonious partnerships, both in love and in business, and is especially helpful for working closely with a relative or friend where positive personal interactions are vital.
Information taken from http://www.crystalvaults.com/crystal-encyclopedia/unakite-jasper
Hope this helps and good luck!