Hollandite
Hollandite is a silvery-gray to black mineral composed of barium and manganese. It occurs as opaque crystals and massive material but the interest in this mineral in the gem trade is as inclusions in Quartz gems. It forms beautiful radiating black “stars” throughout quartz crystals coming from Madagascar. These well-formed Quartz crystals are collected by mineral collectors and rarely faceted into gems prominently displaying the attractive Hollandite stars.
Hollandite is found in these locations: in India, at Kajlidongri and Sitapur, Chhindwara district, Madhya Pradesh; in the Nagpur and Balaghat districts, Maharashtra; at Banswara, Rajasthan; and elsewhere. From Sorharras, Ultevis, Sweden. In Norway, from Tangen, Hurdal. At Langenberg, Saxony, Germany. From Inken, Tiovine region, Morocco. In the USA, in the Artillery Mountains, Mohave County, and in the Apache mine, Sierra Ancha district, Gila County, Arizona. As fine inclusions in Quartz from Madagascar.
| Category: | Oxide minerals |
| Chemical Formula: | Ba(Mn4+,Mn2+)8O16 |
| Barium Manganese Oxide | |
| Molecular Weight: | 852.99 gm |
| Composition: | Barium | 12.88 % | Ba | 14.38 % | BaO |
| Sodium | 0.27 % | Na | 0.36 % | Na2O | |
| Manganese | 42.51 % | Mn | 4.16 % | MnO / 62.17% MnO3 | |
| Aluminum | 0.63 % | Al | 1.20 % | Al2O3 | |
| Iron | 8.51 % | Fe | 12.17 % | Fe2O3 | |
| Silicon | 0.33 % | Sii | 0.70 % | SiO2 | |
| Lead | 4.86 % | Pb | 5.23 % | PbO | |
| Oxygen | 30.01 % | O | |||
| 100.00 % | 100.38 % | = TOTAL OXIDE |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Crystals short prismatic with flat pyramidal termination, to several em; radial fibrous, massive |
| Twinning: | Common on {101} |
| Cleavage: | Distinct/Good, Prismatic |
| Tenacity: | Brittle |
| Moh’s Hardness: | 4.7 – 6.0; VHN = 488-560 || [001], 620-689 – [001] (100 g load) |
| Density: | 4.95 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Black, Grayish Black to Silvery Gray |
| Transparency: | Opaque |
| Luster: | Metallic, Earthy (Dull) |
| Refractive Index: | R1-R2: (400) 31.3-37.7, (420) 31.2-37.4, (440) 31.1-37.1, (460) 30.5-36.5, (480) 29.7-35.9, (500) 29.1-35.0, (520) 28.5-34.2, (540) 27.8-33.1, (560) 27.1-32.2, (580) 26.6-31.5, (600) 26.3-30.9, (620) 26.1-30.4, (640) 25.8-30.0, (660) 25.6-29.5, (680) 25.3-29.0, (700) 25.0-28.4; Biaxial |
| Birefringence: | 0.000 |
| Dispersion: | n/a |
| Pleochroism: | Weak |
| Anisotrophism: | Strong; color in reflected light: White |
