| Labradorite | 1 15 29 45 68 |
| Lamellae, twin | 2 14 29 36 38 40 42 46 53 59 |
| Lamellibranchs | 17 32 40 72 |
| Lamprophyre, mica | 34 |
| Landedwednack | 29 |
| Land's End | 25 |
| LAPWORTH | 38 40 55 |
| Larnaca | 21 |
| LASAULX | 28 |
| Laurvig | 49 |
| Laurvigite | 49 |
| Lava | 31 46 50 |
| LECHERTIER FILS | xxv |
| Leek | 71 |
| LEHMANN | 29 |
| Leicestershire | 38 55 65 |
| Leithakalk | xxii 48 |
| LEMBERG | 64 |
| Lenticles, calcite | 34 38 52 |
| Lepas | 5 |
| Leucite | 27 51 |
| Leucitophyre | 27 |
| Leucoxene | 2 8 9 10 15 16 38 65 66 |
| Leucoxenic dolerite | 15 |
| LEVY | 28 41 44 68 70 |
| Lignite | xxiii |
| Limburg | 41 |
| Limburgite | 41 |
| Limestone, chalky | 21 |
| Limestone, dolomotised | 63 |
| Limestone, endothyra | 71 |
| Limestone, globigerinal | 21 |
| Limestone, lithothamnion | 48 |
| Limestone, oolitic | 17 |
| Limestone, Wenlock | 40 |
| Limonite | 19 27 29 41 42 54 55 67 68 70 |
| Linlithgow | 37 |
| Lion's Haunch | 13 |
| Liparite | 70 |
| Liskeard | 23 |
| LISTER | 48 |
| Liyhophysial | 33 |
| Lithothamnion | 48 |
| Little Carpathian Mountains | 70 |
| Lituolidae | 5 72 |
| Lizard | 29 43 |
| Llanfairpwllgwyngyll | 39 |
| Loch Borolan | 51 |
| 'Locust' | 40 |
| Long Cliff | 65 |
| Longulites | 31 69 |
| Lower Greensand | 32 |
| Ludite | 32 |
| LYDEKKER | 56 |
|