JADEITE - Canadian Institute of Gemmology

25) Vesuvianite. It is also called idocrase. It has a refractive index of 1.70-1.723 and a
hardness of 6 to 7. Garza-Valdés (1993: 117) notes that "it has a low birefringence, and under
crossed polars it often shows anomalous Berlin blue." It is sometimes called "vesuvianite jade". The
green variety known as Californite, which comes from California, is sometimes used as a jadeite
substitute and may be called "American jade" or "California jade". Webster (1975: 232) warns that
Californite "has a jade-like character and may pass for the genuine material, especially as the
density is a little lower than the crystal idocrase and varies between 3.25 and 3.35 thus overlapping
the values for jadeite." However, the refractive indexes of the two stones are different, Californite
being 1.72. Hauff (1993: 87) gives Californite's specific gravity as 3.4.
Walker (1991: 31), reprints a chart from the Spring 1982 issue of Gems and Gemology that
lists the most problematic green jadeite simulants. These are: nephrite, grossularite, Californite,
saussurite, prehnite, bowenite, steatite or soapstone, aventurine (dyed), chrysoprase, glass, and
calcite (dyed).
11. Grading Jadeite
The criteria for evaluating jadeite have evolved largely within China. As Hughes, Galibert, et al
(2000: 2) comment, "jade connoisseurship is almost strictly a Chinese phenomenon." In a section
on the pricing and valuation of jadeite, the web site of the Department of Geology at the University
of Texas (www.geo.utexas.edu) warns that it is "a difficult subject best left to a jade expert." Over
the past couple of decades a number of authors writing in English have discussed the criteria for
evaluating finished jadeite (see Healey and Yu 1983; Ng and Root 1984; Ho 1996; Newman 1998;
Ou Yang 1999; and Hughes, Galibert, et al 2000: 17-20).
Ng and Root (1984: 104-105) provide a color "Jade Master Stone Chart" that divides jadeite
into fifty different categories as well as providing illustrations of more and less desirable
characteristics of jadeite. Thirty-five of the categories are for green stones, five for lavender, and the
remaining ten for other colors. There is a "Color Grading Scale" using letters, from "A" to "E": A =
exceptional. B = very good, C = good, D = fair, and E = acceptable. In addition the stones are given
numbers. In the case of green jadeite in particular, this serves as an additional means of ranking,
from "A1" (which would be called exceptional imperial/emerald green jadeite) to "E7" (which
would be called acceptable melon green jadeite). Newman (1998: 105) reprints a similar chart
provided by Mason-Kay that has only thirty-six categories.
Healey and Yu (1983: 1670) comment in general that "through extensive experience in the
trade most jade dealers have a broad consensus of opinion on how the quality of a piece of jade
should be graded." Hughes, Galibert, et al (2000: 18) have remarked that "while a number of
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