| ULEXITE (Sodium Calcium Borate Hydroxide) | |
| ULLMANNITE (Nickel Antimony Sulfide) | |
| URANINITE (Uranium Oxide) | |
| URANOCIRCITE (Hydrated Barium Uranyl Phosphate) | |
| URANOPHANE (Hydrated Calcium Uranyl Silicate) | |
| URANOPILITE (Hydrated Uranyl Sulfate Hydroxide) | |
| UVAROVITE (Calcium Chromium Silicate) | |
| UVITE (complex Calcium Sodium Magnesium Iron Boro-Aluminum Silicate Hydroxide) |