Grinding is a Processing method which uses a single ingredient and grinds it in a stone mortar and pestle to create ingredients for cooking or other trades. You do not need any tools to grind ingredients, just hitting 'L' by default is enough.
For more advanced grinding, you need to learn the knowledge Grinding: Beginner from Ornella in Heidel City by completing her quest Materials for Equipment Repair. The quest is a part of Learning Higher Processing Skills, which can be obtained in two ways: Have Gathering Apprentice 4 and get the quest directly from Ficy in Heidel City, or complete the questline started by the Black Spirit as you enter Heidel City.
The Black Spirit will ask you to go to Jemkas Wyrmbane, who will have the quest Because I Like You, which requires you to either have Gathering Beginner 7 or have completed the quest Go to the Northern Heidel Quarry.
Complete the rest of the questline to get access to Learning Higher Processing Skills and Ornella's quest:
- Because I Like You
- Nothing Our Friendship Can't Do
- Settling Down in Heidel
- Bustling Alejandro Farm
- Helping With the Pumpkin Harvest
- A Threatening Scarecrow!
- A Meat Dish for the Workers
- In Search of Higher Processing Knowledge...
To obtain Grinding: Skilled you'll need to have done the quests for Heating: Skilled, Chopping: Skilled and Dryng: Skilled. After that, a few quests from Geranoa, a Material Vendor in Calpheon City located in the Market Street district, will be available.
Furthermore, Gems can be ground to extract Black Powder.