Physical Properties of Jade for Identification and Classification Purposes.
This site contains information on the Physical Properties and Chemical Composition of Minerals, gemstones, crystals, precious metals, and sedimentary, igneous and metamorphic rocks for crystallography, geology, identification of minerals, Jewelry and mineralogy. This includes cleavage, description of crystal formations, crystal structure, hardness, specific gravity, Mohs’ Scale, crystal features and crystal habits for identification and classification purposes.
The
stone known as Jade is actually two different stones, Jadeite and
Nephrite. For centuries, the stones were thought to be the same, but with
the advent of crystallography, scientists discovered that though they both
contained Silica in their chemical compositions, Nephrite contained
magnesium and Jadeite contained Aluminum. Because they are close in
chemical composition and both serve the purposes for which they are used,
so most people continue to refer to both of them as Jade. Of course,
geologists, mineralogists and jewelers are sure to distinguish between the
two stones because Jadeite is rarer and hence more valuable than Nephrite.
Jadeite
Chemistry:
NaAlSi2O6 , Sodium Aluminum Silicate
Class:
Silicates
Subclass:
Inosilicates
Group:
Pyroxenes
Luster:
Vitreous.
Transparency:
Examples are generally opaque to translucent
Crystal System: monoclinic;
2/m
Cleavage:
is poor in two directions at near 90 degree angles, but is never seen in
massive specimens
Fracture:
Splintery to Uneven
Hardness:
6.5 – 7 (extremely tough, actually stronger than steel)
Specific Gravity:
approximately 3.3 - 3.5 (above average for translucent minerals)
Streak:
White
Flame Test:
Sodium result-yellow
Best Field Indicators:
Toughness, green color, density, flame test and hardness
Index Of Refraction:
approximately 1.66
Jadeite
Chemical Composition
Jadeite is the very rare chemical combination, NaAlSi2O6, Sodium Aluminum
Silicate, which is very close to the very common minerals, Albite,
NaAlSi3O8, and Nepheline, NaAlSiO4. However, because of the extreme force
under which Jadeite forms, its specific gravity (3.3-3.5) is much higher
than that of Albite (2.61) or Nepheline (2.60 - 2.65).
Jadeite
Geological Environment
Jadeite is rarely found in its original geological environment; most
specimens are found in river
gravels and boulders. It forms in zones that have experienced the extreme
forces of continent to continent contact. In theses collisions, Albite
loses a SiO2 molecule to form a Quartz and Jadeite.
Jadeite
Crystal Structure/habit
Most Jadeite occurs as very tough massive specimens of tightly interlocked
crystals in; crystals of the mineral are rare but exhibit the Monoclinic
system of three axes of unequal lengths, two perpendicular to each other
while the third intersects the plane of the other two at an angle inclined
to one of them and at a 90 degree angle to the last one. Jadeite does
occur as granules in metamorphic rocks.
Jadeite
Color
Although famous for its green, pure jade is actually white, with
impurities forming green, red, yellow, pink, white, violet, orange,
blue-green and brown. Jadeite is usually more vivid in color than
Nephrite. Jadeite is the only one of the two that produces the highly
prized emerald green Jade called Imperial Jade. Jadeite gets this emerald
color from chromium. Other colors are also formed from impurities. Brown
indicates the presence of iron and Violet, manganese.
Jadeite
Uses
Its toughness made it ideal for use by Natives of Central America as axes,
knives, weapons and ornamentation for centuries. Modern uses include
carvings and jewelry.
Nephrite
Chemistry:
Ca2(Mg,Fe)5(OH)2(Si4O11)2
, avariety
of actinolite.
Index Of Refraction:
1.62 (nephrite)
Hardness:
6.5 - 7
Cleavage:
n/a-massive stone
Crystal System:
monoclinic
Nephrite
Color
Pure Nephrite is white. Nephrite is usually
green or creamy white, but can also be beige, yellow, blue or black and
often contains veins of color. The presence of iron provides the green in
nephrite.
Nephrite
Uses
Nephrite’s uses include jewelry, carvings and bowls and vases.
Because of its toughness, ancient cultures used it to make symbolic
ornaments, axes, knives and weapons.
Jade
Imitators
When Jade is sold under names such as New Jade, Korean Jade, Stygian
Jade, Pagoda stone, Mexican Jade, and Indian Jade, it is most often
fake. Jewelers may also dye poor quality jade to enhance the color.
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