Jamborite

The crystals are so tightly packed it almost looks fuzzy.
Overview
Jamborite is a mineral that can be found in the Geode and the Omni Geode. As a mineral, it can be collected by cracking open these geodes and then kept as part of the player’s mineral collection or used for crafting-related purposes.
Its main practical uses are in tailoring and dyeing. When placed in the spool of the Sewing Machine, Jamborite creates the Green Thumb Shirt. It can also be used as a green dye ingredient at the dye pots in Emily’s and Haley’s house at 2 Willow Lane.
Because Jamborite serves as both a mineral and a dye item, it is worth saving at least one copy if you plan to use the Sewing Machine or want access to green dye options. Additional copies can be kept for later tailoring projects, while extras beyond that can be treated like most surplus minerals once those uses are covered.
Official description
The crystals are so tightly packed it almost looks fuzzy.