Epidote Crystal with Pleochroism, Color Change, from Shigar Valley, Gilgit-Baltistan, Pakistan.

https://www.oldearthminerals.com/shop/p/pleochroic-epidote-crystal-color-changing-pakistan

Epidote (Pleochroic) - Green Monster Mountain, Prince of Wales Island, Alaska, USA.  NFS, Personal Collection.  Collected July 2016. Extremely rare to see transparent crystals of Epidote from Green Monster.  The locality is known for its large crystals, however even the small crystals are unable to pass light, presumably from a higher iron content.  The mine owner jumped in his chair when I showed him I had found a gemmy crystal on his table.  The crystal exhibits 3 different types of terminations and a healed bottom.

Watch the color change as the crystal is turned!

Pleochroic Epidote Crystal.

https://oldearthminerals.etsy.com/listing/1590827230

https://www.oldearthminerals.com/shop/p/qb2w8m9xhfmew597jp5pjp7xxvo1sb-f4nbg-pzwlf-pby7f

Kunzite, with Tourmaline

The beautiful pink to violet variety of the lithium silicate pyroxene group mineral spodumene is a relatively recent addition to the gem inventory. It was first described in 1902 by the gem and mineral dealer G.F. Kunz (who worked, amongst others, with Tiffany's, the Smithsonian and assembling J.P. Morgan's world class mineral collection) after its initial discovery in California famous Pala district pegmatites. Crystal surfaces are often covered in triangular arrowhead shaped etch pits where the crystal was dissolved by hydrothermal fluids during its residence in the mother rock.

The mineral is strongly pleochroic, displaying three different colours depending on the orientation from which it is viewed. This is due to the different pathways rays of light take within the crystal when they are refracted and split into 3, resulting in different absorptions and residual colours visible to the eye. As a result, gem cutters have to be sure to cut it in the correct orientation to display the deeper violetish hue through the top table facet rather than the pale pink to colourless one. Though it has decent hardness (6.5-7 on Mohs scale), faceting is complicated by the mineral's perfect easy cleavage, where the crystal splits along lines of weakness with fewer atomic bonds in the crystal structure.

The best examples come from the pegmatite fields of Nuristan in Afghanistan, and display strong violet, pale pink and pale green shades. Other localities include Madagascar, Brazil and the USA. Most kunzites are quite pale, and more saturated shades (due to substitution impurities of manganese in the crystal structure) are quite rare. It is one of the few gems available in large sizes relatively inclusion free at reasonable cost. Quality depends on depth of colour and clarity, and the larger the stone, the deeper the colour. Crystals in the Black HIlls of Dakota have been found up to 14.3 metres long. The largest cut gem weighs 880 carats and is held by the Smithsonian Institution.

The colour can slowly fade in direct sunlight, so wearing it for prolonged periods under Sol's rays is not advised. Some specimens have been heated or irradiated to enhance the colour. In this amazing 9.7 x 3.7 x 3.0 cm specimen from Nuristan mined in the 1970's in Afghanistan the somewhat ordinary oblong of Spodumene has a series of gemmy pink Tourmaline crystals growing out of it in a beautiful steamboat fan.

Loz

Image credit: Joe Budd/Rob Lavinsky/iRocks.com