| Montroydite | |
| Category: | Oxide mineral |
| Formula: | HgO |
| Imasymbol: | Mtyd[1] |
| Strunz: | 4.AC.15 |
| System: | Orthorhombic |
| Class: | Dipyramidal (mmm) H-M Symbol: (2/m 2/m 2/m) |
| Unit Cell: | a = 5.52 Å, b = 6.6 Å, c = 3.52 Å; Z=4 |
| Color: | Deep red, brownish red to brown |
| Habit: | Long prismatic, equant, rarely flattened; striated; massive to vermicular clusters |
| Cleavage: | Perfect |
| Tenacity: | Sectile |
| Mohs: | 1.5 - 2.0 |
| Luster: | Sub-adamantine, vitreous |
| Streak: | Yellow brown |
| Diaphaneity: | Transparent to translucent |
| Gravity: | 11.23 |
| Opticalprop: | Biaxial (+) |
| Refractive: | nα = 2.370 nβ = 2.500 nγ = 2.650 |
| Birefringence: | δ = 0.280 |
| Pleochroism: | Deep red-orange to yellowish brown (visible in thick sections) |
| 2V: | Large |
| References: | [2] [3] |
Montroydite is the mineral form of mercury(II) oxide with formula HgO. It is a rare mercury mineral. It was first described for an occurrence in the mercury deposit at Terlingua, Texas and named for Montroyd Sharp who was an owner of the deposit.[2]
Montroydite occurs in mercury deposits of hydrothermal origin. Associated minerals include: native mercury, cinnabar, metacinnabar, calomel, eglestonite, terlinguaite, mosesite, kleinite, edgarbaileyite, gypsum, calcite and dolomite.[3]