Table 1. Crystallographic data of the candidate pseudo-hexagonal minerals.
The columns contain the crystal system S (O = orthorhombic, M = monoclinic), the unit-cell parameters (a, b, c, β), the pinacoid face entering the pseudo-hexagonal morphology and the corresponding prism faces. The last two columns contain, respectively, the pinacoid/prism angle and the prism/prism angle. For aragonite, the (110) penetration and contact twins have been used for calculations. In the penetration twin, the ‘pinacoid face’ is made of two slightly misoriented (110) faces having the average orientation of the (010) pinacoid. In the contact twin, the faces labeled ‘pinacoid’ are the (110) faces of the next individual of the twin (*). See Fig. 7 ▸ for further discussion
| Mineral | S | a | b | c | β | pin | pri1 | pri2 | pin^pri | pri1^pri2 |
|---|---|---|---|---|---|---|---|---|---|---|
| Barite | O | 8.8842 | 5.4559 | 7.1569 | 90 | (001) | (011) | (01 ) |
52.6807 | 74.6385 |
| Celestine | O | 8.3770 | 5.3500 | 6.8730 | 90 | (001) | (011) | (01) |
52.1025 | 75.7950 |
| Gypsum | M | 6.2840 | 15.2000 | 6.5230 | 127.410 | (010) | (120) | (1 0) |
56.7044 | 66.5912 |
| Mirabilite | M | 1.5120 | 10.3700 | 12.8470 | 107.789 | (010) | (110) | (10) |
43.4114 | 86.8228 |
| Aragonite (penetration) | O | 4.9614 | 7.9671 | 5.7404 | 90 | (010) | (110) | (10) |
58.0880 | 63.8240 |
| Aragonite (contact) | O | 4.9614 | 7.9671 | 5.7404 | 90 | (110)* | (110) | (10) |
52.352 | 63.8240 |
| Strontianite | O | 5.1075 | 8.4138 | 6.0269 | 90 | (010) | (10) |
(
0) |
58.7407 | 62.5186 |
| Nahcolite | M | 7.5100 | 9.7000 | 3.5300 | 93.320 | (010) | (110) | (10) |
52.2986 | 75.4028 |
| Borax | M | 1.8580 | 10.6740 | 12.1970 | 106.680 | (010) | (10) |
(
0) |
43.2191 | 93.5617 |