Ludlamite
Ludlamite is a phosphate mineral that produces beautiful specimens characterized by bright, apple green groups of crystals that typically form as sprays of radiating, jaggedly pointed, crystals that resemble sheaves of wheat.
Ludlamite is unusual in that it is a diamagnetic mineral. Diamagnetism is a form of magnetism where certain minerals are repelled by an externally applied magnetic field, and form internal induced magnetic fields in the direction opposite to that of the applied magnetic field. In contrast with this behavior, some minerals, such as Xenotime, are paramagnetic. Paramagnetism is a form of magnetism where certain minerals are attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field.
Ludlamite was named in 1877 by English geologist Nevil Story Maskelyne (1823–1911) and English chemist Frederick Field (1826-1885) in honor of their friend, English mineral collector Henry Ludlam (1824-1880), London, England. Ludlamitewas first described in 1877 for an occurrence at the Wheal Jane Mine, St. Day District, Cornwall, England.
There are only a few locations for facetable crystals. These include the Wheal Jane Mine, Truro, Cornwall, England (the Type Locality); Morococala and Huanuni, Oruro, Bolivia; Rapid Creek, Yukon Territory, Canada; Hagendorf, Bavaria, Germany; San Antonio mine, Santa Eulalia district, Chihuahua, Mexico; the Blackbird mine, Lemhi County, Idaho, USA; the Palermo #1 mine, North Groton, Grafton County, New Hampshire; and Custer County, South Dakota, USA.
| Category: | Phosphate mineral |
| Chemical Formula: | (Fe2+,Mg,Mn2+)3(PO4)2 • 4H2O |
| Hydrated Iron Magnesium Manganese Phosphate | |
| Molecular Weight: | 400.88 gm |
| Composition: | Magnesium | 5.46 % | Mg | 9.05 % | MgO |
| Manganese | 4.11 % | Mn | 5.31 % | MnO | |
| Iron | 25.08 % | Fe | 32.26 % | FeO | |
| Phosphorus | 15.45 % | P | 35.41 % | P2O5 | |
| Hydrogen | 2.01 % | H | 17.98 % | H2O | |
| Oxygen | 47.89 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | As crystals, usually tabular, to 9 cm, may be in parallel groups; granular, massive. |
| Twinning: | None |
| Cleavage: | Perfect on [001], Indistinct on [100] |
| Fracture: | Conchoidal |
| Tenacity: | Slightly brittle |
| Moh’s Hardness: | 3.5 |
| Density: | 3.12 – 3.19 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioacitve |
| Other: | Diamagnetic. Soluble in acids. |
| Color: | Apple-Green to bright Green; nearly Colorless in transmitted light |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous, Pearly on cleavage [001] |
| Refractive Index: | 1.650 – 1.697 Biaxial ( + ) |
| Birefringence: | 0.038 – 0.044 |
| Dispersion: | Perceptible; r > v |
| Pleochroism: | None |
