Jade
Covers jadeite and Nephrite. Both are metamorphic and form at subduction zones near convergent tectonic-plate boundaries. They form at different pressures so do not occur together. Both consist of tightly interlocked microscopic fibes that impart toughness. High fracture-resistence so good for axes, hammers and knives in neolithic times.
Imperial jade: very transl., strong bright emerald green colour. Used for jewellery, sculpture and carvings. Has soft limpidity. Highly prized and can be some of the most exp. gemstones.
Jadeite: Mohs' 7 , hard & tough. Minute intergrown granular and fibrous crystals. White, green & violet (rare). Often used as cabochons and carvings. Commonly treated by dyeing. Sodium aluminium iron silicate. A pyroxene mineral once known as Burmese jade. Most recently used in China.
Nephrite: Carvings are popular in Chinese culture and date back 1000s of years. Moh's 6.5 but similar crystal structure so still tough. Dark green, brown, grey, white. Generally reserved for carvings. Hydrated calcium magnesium iron silicate. By 2000 BC Chinese had associated five virtues with nephrite: humanity for its smoothness, justice for its translucency, wisdom for the sound made when stuck with metal, courage for its hardness and honesty for its purity.
Hotan nephrite: Consists almost entirely of the mineral tremolite and contains, on average, 3% impurities, (mainly iron, chromium and graphite) to produce colours of creamy white to shade of green, yellow, lavender, grey and black. Is graded by hue, saturation , tone and translucency. ideally colour distribution should be even with minimal zoning; thin or watery colours are less desirable. Top grades are highly translucent and reflect light with a soft glow that makes the stone appear luminescent. The finer the tremolite fibres, the smoother the texture - fiber alignment is key to softness of the lustre. Most highly valued is 'mutton fat' - highly translucent, creamy-white that is 99% pure tremolite.
Hotan once referred to as Hetian jade. A popular name in the 1700s. Initially referred to nephrite from the White Jade and Black Jade rivers at Hotan, but came to refer to all nephrite jade from China, Russia dn Korea. In 2010 Chinese government revised its national standards for jade names and removed geographical origin from the formal description of Hetian jade, Today any nephrite jade can legally be called Hetian but Hotan refers specifically to hade from the White and Black Jade rivers.
Lore: magical properties to preserve body, invoke the dead, banish evil, bring rain, protect from heat, cold, hunger; jade bowls bring energy to food and drink.
'Gems and the new science: matter and value in the scientific revolution' by Michael Mycroft, Chicago, University of Chicago Press, 2026: Silk Road - Buddhist kingdom of Khotan, 1st Millennium, between two rivers Karakash and Yurungkash was a region famous for nephrite jade, sourced from the rivers. The Kingdom was destroyed in AD1006.
Arab Roots of Gemolgy
Some elements from 'Arab roots of gemolgy: Ahmad ibn Yusuf Al Tifaschi's Best Thoughts on the Best of Stones' (c.1240) trans. Samar Najm Abul Huda. The Scarecrow Press, London, 1998.
Nephrite is a silver based stone - formed in silver mines from vapours still not condensed into silver. Found in Kashgar, between China and the town of Ghaznah, their language being Turkish. Some stones are manufactured in India and sold as nephrite, while in fact they are not.
Nephrite has two varieties:
- white one, manufactured in China from a mix of substances and does not possess any of the properties of nephrite except that it looks like it
- yellow one, like that of ivory, this is the good, genuine mineral variety
Lightening never hits a place where this stone is present - lighthouses, in Persian lands, were built where this stone was hung well in sight; it decreases the recurrance of erotic dreams; beneficial for pain in the stomach if hung on it extenally.
Nephrite is made into bowls in China. Also made into finger-rings.
