| Lansfordite | |
| Category: | Carbonates |
| Imasymbol: | Lfd[1] |
| Molweight: | 174.39 |
| Strunz: | 5/D.01-30 |
| Dana: | 15.1.6.1 |
| System: | Monoclinic |
| Symmetry: | P21/c (No. 14) |
| Unit Cell: | a=7.3458 Å, b=7.6232 Å, c=12.4737 Å, β=101.722° |
| Colour: | Colourless, white after exposure |
| Habit: | Crystals, stalactites terminated by crystal faces, efflorescences, parallel growths. |
| Cleavage: | Perfect, Distinct |
| Mohs: | 2.5 |
| Luster: | Vitreous (if fresh) |
| Streak: | White |
| Diaphaneity: | Translucent, opaque after exposure |
| Gravity: | 1.6 |
| Density: | 1.6 |
| Birefringence: | 0.042 |
Lansfordite is a hydrated magnesium carbonate mineral with composition: MgCO3·5H2O.[2] Landsfordite was discovered in 1888 in a coal mine in Lansford, Pennsylvania. It crystallizes in the monoclinic system (space group P21/c[3]) and typically occurs as colorless to white prismatic crystals and stalactitic masses.[4] It is a soft mineral, Mohs hardness of 2.5, with a low specific gravity of 1.7. It is transparent to translucent with refractive indices of 1.46 to 1.51.[5] The mineral will effloresce at room temperature, producing nesquehonite.[6]