JADEITE - Canadian Institute of Gemmology

associated with large and possibly active fault zones that are major crustal boundaries (e.g., the San
Andreas Fault) and involve mostly horizontal motion" and "most jadeite rocks occur in relatively
young geologic terrain, Cretaceous age or younger (less than 100 million years)." In sum, Harlow
(1993: 14) argues that "these facts strongly suggest a genetic relationship between plate tectonics...
and the formation and surface appearance of jadeite rock."
Burma. Most of the jadeite produced in the world at present comes from northern Burma.
This has been the sole source of fine "Imperial" jadeite for several centuries. Bender (1983)
describes the geology of the jadeite mining region in Burma. It is characterized by an extensive
broken outcropping containing bodies of serpentinized peridotite (their age ranging from Late
Cretaceous to Eocene). The serpentinites found here are surrounded by crystalline schists and
plutonic rocks (such as granites and monzonites). Jadeite was formed independently of the
intrusives by crystallization from hydrous fluids (there were derived by dewatering of the subducted
Indian plate) that rose along fractures in the serpentinized peridotite at relatively high-pressure and
low-temperature during the Tertiary formation of the Himalayas. Fluids that form in these special
conditions are saturated with sodium aluminosilicates. The passage of these fluids through
serpentinites generated jadeitite, albite-nephaline, and albitite dikes (jadeite being generated at higher
pressure and albite at lower pressure). The dikes commonly have central zones of jadeite and outer
rims of chlorite and amphibolite at the point of contact with the serpentinites (see Harlow and Olds
1987).
This region commonly is referred to as the "Jade Tract" or "Jade Land." The latter term is
roughly equivalent to the Burmese term for the region: Kyaukseinmyo.It is a rugged plateau located
over 400 kilometers north of Mandalay. The main river in the area is the Uru, which serves roughly
as the eastern boundary of the Jade Tract. The most important mining area in the region is located at
Tawmaw (see Chhibber 1934: fig. 1, pg. 25), about 120 kilometers northwest of Mogaung. Mining
has been going on in the Tawmaw area at least since the nineteenth century and Tawnaw is a source
of most major varieties and colors of jadeite. Most of the jadeite from this area comes from
secondary deposits in the Uru Boulder Conglomerate. The conglomerate is exposed over an area
ranging in width from three to over six kilometers (the widest point being at Mamon) and up to 300
meters thick (see Chhibber 1934). There are a number of secondary deposits located west of the
Uru River, such as those at Sate Mu, Hpakangyi (adjacent to Hpakan), and Maw-sisa.
The town of Mogaung served as the primary jadeite trading center throughout most of the
modern history of jadeite mining in the Jade Tract. Mogaung is located a little over 100 kilometers
west of Myitkyina town. It served as a collection and storage center for rough jadeite. Here the
material was graded prior to shipping. The importance of Mogaung has declined and Hpakan (also
spelled Hpakant, Phakan, or Phakant) has emerged as the primary center in recent years. Hpakan
lies along the Uru River some sixteen kilometers by road from Tawmaw.
23