Diamond Mine Mini-Storage Share: General Services Diamond Mine Mini-Storage Visit Website 4400 Horner Street Union City, CA 94587 (510) 489-4747 (510) 489-4788 (fax) About Map About A family-owned and operated self-storage company dedicted to providing the highest quality storage exerpience in the industry. What's Nearby? Distance: 5 10 15 20 25 50 mi.