Pietersite

Pietersite is an ornamental stone with a brecciated texture, made of angular fragments in blue-grey, golden yellow, brown and brownish red. Like tiger's eye, it contains crocidolite (blue asbestos) fibres embedded in fine-grained quartz, and these fibres create its shimmer. But because the fibres point in a different direction in each fragment, the light does not move as a single band, as in tiger's eye, but as irregular flashes flowing every which way like brush strokes. It is named after Sid Pieters, the mineral dealer who found it in Namibia in 1962. Its only known sources are Namibia and China.

Jewellery: it is mostly cut as cabochons and made into pendants, ring stones and earrings. Decorative objects: it is sold as decorative slices, carvings and polished palm stones to hold in the hand. Collecting: because it is rare and comes from only two countries, collectors seek it out.

It has a hardness of 7 on the Mohs scale. It scratches glass and steel; a steel knife cannot scratch it. Its specific gravity is 2.5–2.74 g/cm³.

Its best-known localities: Hopewell Farm near Outjo, Kunene Region, Namibia; Xichuan County, Nanyang, Henan, China.

Turned in the light, the shimmer does not glide as one band; it flashes on and off separately in angular fragments facing different ways, recalling a stormy sky or paint strokes flowing in many directions. Angular fragments from a few millimetres to about a centimetre across can be seen, with white flecks of calcite or veins of colourless chalcedony between them. Namibian pietersite is dominated by blue-grey and golden yellow areas; Chinese pietersite has an overall jasper-like brownish red colour and a weaker shimmer.

On the “street to diamond” value ladder it sits on step 6 of nine: Fine ornamental and collector stone. Pietersite is a rare stone: it has only two known sources, and according to a GIA study published in 2010 both mines appear to be closed; the minable stock in Namibia was reported to be largely depleted in the 1990s. Its value depends mostly on how vivid and widespread the shimmer is, how well the blue and golden colours go together, and how striking the pattern is. Namibian pietersite is generally considered superior to material from China because of its more vivid colours. Crack-free, well-polished pieces whose shimmer has not been dulled by iron oxides are the most sought after.

Crystal-therapy sources claim that pietersite holds “the keys to the kingdom of heaven”; the phrase is also repeated in a magazine article published in Namibia. The same sources claim that the stone supports willpower and strengthens a person's inner guidance and ability to recognise truths. There is no scientific evidence that pietersite strengthens willpower, intuition or spiritual insight; its “stormy” look comes from asbestos fibres lying in different directions and reflecting light. Rough stone contains asbestos fibres, so it should not be cut or ground into powder at home. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.

Pietersite contains fibres of crocidolite, an asbestos mineral. Because the fibres are locked inside hard quartz, wearing and handling polished stones is harmless. Dust produced when cutting, grinding or sanding rough material, however, should not be inhaled: work wet and wear a suitable dust mask.