Introduction: dravite is a magnesium-rich, alkali tourmaline (see tourmaline entry for details of the various tourmaline groups) that forms a series with schorl (iron-rich alkali tourmaline). It is found typically in metamorphic or skarn-type mineral assemblages and is often associated with axinite and datolite. The boron is introduced into the rock by fluids (metasomatism) and in most cases, granite magma is thought to be the source of the boron.

Occurrence in Wales: although several occurrences of tourmaline have been reported from Wales (see tourmaline entry), a lack of detailed optical or analytical data has precluded most of these from being classified to mineral species level. New data (National Museum of Wales/A.J. Tindle, unpublished data) confirms the presence of dravite in at least two of these occurrences. As dravite can be further divided into fluor- hydroxyl- or oxy varieties, depending on the filling of the W site in the crystals lattice, microprobe analyses have also established that the Welsh dravites are dominated by hydroxyl anions and therefore can be termed hydroxyl-dravite (although this classification, proposed by Hawthorne & Henry (1999), has not been formally accepted by the IMA). As more microprobe data becomes available it is anticipated that a more widespread distribution of dravite in Wales will be demonstrated.

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