Opal

Its internal structure causes it to reflect a rainbow of light.
Overview
Opal is a mineral that can be found in the Frozen Geode and the Omni Geode. It is one of the geode minerals the player may uncover while processing geodes, making it a possible early- to mid-game collectible when mining and cracking geodes at the Blacksmith.
Opal also has two practical uses beyond being sold or kept as part of a collection. It is used in the spool of the Sewing Machine to create a Shirt, and it can be used in dyeing as a blue dye at the dye pots in Emily’s and Haley’s house at 2 Willow Lane. This makes it useful both for tailoring and for color customization.
- Source: Frozen Geode, Omni Geode
- Tailoring use: Shirt
- Dyeing use: blue dye
Official description
Its internal structure causes it to reflect a rainbow of light.