This content comes from Rangers of Porphyra

Elfstone (blue, green, white and yellow)
Aura moderate abjuration; CL 7th
Slot neck; Price 8,400 gp; Weight
Description
These beautiful pieces of jewelry contain a brilliant gem of varying color, based on the territory of the recipient, typically being given to rangers who have given service to elven communities. The setting is always silver, and in the shape of an eagle, and is intended to be used as a cloak clasp. Elfstones grant a +1 deflection bonus to the wearer, which increases to +2 if the wearer is in their primary (first) favored terrain, and that terrain matches the elfstone’s color; blue—plains, green—forest, white—water, yellow—desert. The wearer also gains a +2 competence bonus to skill and ability checks if they in the indicated favored terrain as follows: blue—Strength and Dexterity checks and based skills, green—Intelligence checks and based skills, white—Wisdom checks and based skills, yellow—Charisma checks and based skills.
Construction
Requirements Craft Wondrous Item, karmic blessing, shield of faith, creator must be an elf; Cost 4,200 gp