| Howlite | |
|---|---|
 | |
| General | |
| Category | Inoborates |
| Formula (repeating unit) | Ca2B5SiO9(OH)5 |
| IMA symbol | How[1] |
| Strunz classification | 6.CB.20 |
| Dana classification | 25.3.5.1 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/c |
| Unit cell | a = 12.82 Å, b = 9.351(1) Å c = 8.608(2) Å; β = 104.84(2)°; Z = 4 |
| Identification | |
| Color | White, colorless |
| Crystal habit | Massive to nodular, occurs as tabular prisms flattened parallel to [100] |
| Cleavage | None |
| Fracture | Conchoidal, uneven |
| Mohs scale hardness | 3.5 |
| Luster | Subvitreous, glimmering |
| Streak | white |
| Diaphaneity | Translucent |
| Specific gravity | 2.53 – 2.59 |
| Optical properties | Biaxial (−), colorless (transmitted light) |
| Refractive index | nα = 1.583 – 1.586 nβ = 1.596 – 1.598 nγ = 1.600 |
| Birefringence | δ = 0.017 |
| 2V angle | 73° |
| References | [2][3][4] |
Howlite, a calcium borosilicate hydroxide (Ca2B5SiO9(OH)5), is a borate mineral found in evaporite deposits.[5]
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ "Handbook of Mineralogy" (PDF).
- ^ "Howlite: Howlite mineral information and data". www.mindat.org.
- ^ Barthelmy, Dave. "Howlite Mineral Data". webmineral.com.
- ^ Howlite at Mineral Galleries