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| Hureaulite | |
| Category: | Phosphate minerals |
| Imasymbol: | Hur[1] |
| Molweight: | 728.65 g/mol |
| Strunz: | 8.CB.10 (10 ed) 7/C.04-10 (8 ed) |
| Dana: | 39.2.1.1 |
| System: | Monoclinic |
| Class: | Prismatic (2/m) (same H-M symbol) |
| Symmetry: | C2/c |
| Unit Cell: | a = 17.594(10) Å b = 9.086(5) Å c = 9.404(5) Å β = 96.67(8)°; Z = 4 |
| Colour: | Orange, red, yellow, brown, grey or nearly colourless |
| Habit: | Crystals are short prismatic parallel to (100) or equant, sometimes thick tabular, also massive or imperfectly fibrous[2] |
| Cleavage: | good |
| Fracture: | Uneven |
| Tenacity: | Brittle |
| Mohs: | 3.5 |
| Lustre: | Vitreous to greasy |
| Refractive: | nα = 1.640 – 1.654 nβ = 1.649 – 1.659 nγ = 1.655 – 1.662 |
| Opticalprop: | Biaxial (−) |
| 2V: | greater than 60° |
| Dispersion: | r |
| Birefringence: | δ = 0.012 |
| Pleochroism: | X colourless, Y yellow to pale rose, Z reddish yellow to reddish brown |
| Streak: | Nearly white |
| Gravity: | 3.18–3.2 (measured), 3.23 (calculated) |
| Solubility: | Easily soluble in acids. |
| Diaphaneity: | Transparent to translucent |
| References: | [3] [4] [5] [6] |
Hureaulite is a manganese phosphate with the formula . It was discovered in 1825 and named in 1826 for the type locality, Les Hureaux, Saint-Sylvestre, Haute-Vienne, Limousin, France. It is sometimes written as huréaulite, but the IMA does not recommend this for English language text.[7]
A complete series exists from lithiophilite, to triphylite,, including hureaulite, strengite,, stewartite,, and sicklerite, .[8]
Hureaulite is a secondary mineral occurring in granite pegmatites.[6] At the type locality it occurs in a zone of altered triphylite,, in pegmatite. Typically occurs very late in the sequence of formation of secondary phosphate minerals.[9] Associated at the type locality with vivianite, ; rockbridgeite, ; heterosite, and cacoxenite, . It can be synthesised;[10] most natural hureaulites are Mn-rich compounds but extensive solution is known for synthetic material.[9]
The type locality is Les Hureaux, Saint-Sylvestre, Haute-Vienne, Limousin, France. Hureaulite is also found in a granite pegmatite known for its phosphates in the Aimorés pegmatite district, at the Cigana claim in Galiléia, Doce valley, Minas Gerais, Brazil, formerly known as the Jocão Mine.[4]