Howlite
Ca2SiB5O9(OH)5IMA symbol: Howgrandfathered
Howlite is a borate mineral with the formula Ca2SiB5O9(OH)5, crystallizing in the monoclinic system. It has a Mohs hardness of 3-5, typically white in color, with a vitreous luster, a specific gravity of 2.55. Its streak is white.
Photos
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Crystallography
| Crystal system | monoclinic crystal systemWikidata (CC0) |
|---|---|
| Space group | P 1 21/c 1 |
| Cell (Å, °) | a = 12.82, b = 9.351, c = 8.608; α = 90, β = 104.84, γ = 90 |
| Cell volume | 997.505 ų, Z = 4 |
| Axial ratios | 1.3710:1:0.9205calculated from COD 9001174 |
| Source structure | COD 9001174 (American Mineralogist, 1988) — 1 of 2 structures |
Powder X-ray diffraction (calculated)
| d (Å) | 3.899 | 6.216 | 3.103 | 3.019 | 2.036 | 2.659 |
|---|---|---|---|---|---|---|
| I/I₀ | 100 | 99.5 | 54.5 | 42.4 | 41.3 | 40 |
xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9001174; idealized occupancies, no preferred orientation.
Physical properties
| Density (calculated) | 2.606 g/cm³calculated from COD 9001174 |
|---|---|
| Hardness (Mohs) | 3-5single sourceDana, System of Mineralogy, 6th ed. (1892) |
| Specific gravity | 2.55 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892) |
| Color | whitesingle sourceDana, System of Mineralogy, 6th ed. (1892) |
| Streak | whitesingle sourceWikidata (CC0) |
| Luster | vitreoussingle sourceDana, System of Mineralogy, 6th ed. (1892) |
Chemistry (calculated)
| Molecular weight | 391.33 g/molcalculated from the IMA formula |
|---|---|
| Composition (wt%) | Ca 20.48%, Si 7.18%, B 13.81%, O 57.24%, H 1.29% |
Classification
| Nickel-Strunz (10th) | 6.CB.20Wikidata (CC0) |
|---|---|
| Nickel-Strunz (9th) | 6.CB.20Wikidata (CC0) |
| Dana (8th) | 25.3.5.1Wikidata (CC0) |