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Harmotome from
Allt Tighe Cumhaig, Struy, Strathglass, Aird and Loch Ness, Highland, Scotland, UK
| Classification | ||
|---|---|---|
| Species: | Harmotome | |
| Formula: | Ba2(Si12Al4)O32 · 12H2O | |
| Comments: | The crystals are small, up to 5 mm., but are very beautiful, exhibiting various modifications of the characteristic complex cruciform twins. The harmotome crystals are emplanted on crystals of blende, on baryte or calcite, and sometimes directly on the pink felspathic rock itself. Sprinkled on them and also included in them are minute crystals of pyrite and marcasite. Harmotome, a mineral formed during the very last phases of hydrothermal action, occurs here as elsewhere in veins containing baryte which have an igneous rock for one or both walls, in this case, one wall being a pegmatite. The mineral exhibits a remarkable resistance to weathering; hence the freshness of the crystals, despite having lain so long on the dumps. | |
| Habit: | often doubly terminated, the appearance of the terminations varying much, depending on the relative development of (100) or (110); likewise, the re-entrant angle of (001) may be very prominent or insignificantly developed. The (100) faces are striated parallel to their intersections with (010); their terminal edges are, however, often slightly inclined away from the centre of the cross, and when this is the case the faces are seen to be fluted in two directions, the upper portion parallel to the intersection with (010), the lower parallel with (001), a step-like medial line forming the boundary between the two and suggesting oscillation between (100) and (001) in the lower half. On (010) the medial line is generally very distinct and slightly raised; the characteristic herringbone striae, though often distinct, are by no means always visible. Optical examination of this face shows how very complex the crystals are, the sectors overlapping in a most irregular manner with erratic lines of junction. Associated with the cruciform twins there are smaller 1 1/2 mm. water-clear crystals, combinations of (001), (100), and (010). On these crystals, the striae on (100) are considerably out of parallel with the intersection with (010). | |
| Colour: | colourless | |
| Confirmation | ||
| Validity: | Believed Valid | |
| Data | ||
| Mineral Data: | Click here to view Harmotome data | |
| Locality Data: | Click here to view Allt Tighe Cumhaig, Struy, Strathglass, Aird and Loch Ness, Highland, Scotland, UK | |
| Data Identifiers | ||
| Mindat Occurrence Record ID: | 16339 | |
| Long-form Identifier: | 1:3:16339:0 | |
| GUID (UUID V4): | 0 | |
| Nearest other occurrences of Harmotome | ||
| 1.2km (0.8 miles) | ⓘLoch na Meine Mine, Strathglass, Aird and Loch Ness, Highland, Scotland, UK | |
| 13.7km (8.5 miles) | ⓘGuisachan Quarry, Tomich, North， West and Central Sutherland, Highland, Scotland, UK | |
| 90.4km (56.2 miles) | ⓘBellsgrove Mine (Bellsgrove Opencut), Strontian, Fort William and Ardnamurchan, Highland, Scotland, UK | |
| 90.6km (56.3 miles) | ⓘBellsgrove Quarry (Strontian Barytes Mine; Middleshop mine), Strontian, Fort William and Ardnamurchan, Highland, Scotland, UK | |
| 90.9km (56.5 miles) | ⓘClashgorm Mine, Strontian, Fort William and Ardnamurchan, Highland, Scotland, UK | |
| 91.4km (56.8 miles) | ⓘWhitesmith Mine, Strontian, Fort William and Ardnamurchan, Highland, Scotland, UK | |
| 92.7km (57.6 miles) | ⓘCorrantee Mine, Strontian, Fort William and Ardnamurchan, Highland, Scotland, UK | |
| 95.2km (59.1 miles) | ⓘStrontian, Fort William and Ardnamurchan, Highland, Scotland, UK | |
| References | ||
Allt Tighe Cumhaig, Struy, Strathglass, Aird and Loch Ness, Highland, Scotland, UK