Vera B and All, You have asked a very complex question. Several
mineral groups can look just like each other and still be quite
different. All the data I am about to give you comes from the book
"Description of Gem Materials" third edition by Glenn and Martha
Vargas. Jadeite is sodium aluminum silicate. Hardness 6.5 - 7,
fracture is splintery, streak is uncolored. Colors are white, gray,
green, blue, purple, reddish, and black. I have also seen yellow.
The stone is almost transparent to opaque and the feel is greasy to
vitreous. Nephrite is the second kind of jade. The chemical formula
is hydrous calcium magnesium iron silicate. Hardness is 6-6.5, the
fracture is splintery and the streak is uncolored. Colors are white,
shades of green, reddish, and black. The stone is translucent to
opaque. Luster is dull. Serpentine is the jade look a like. The
chemical formula is basic magnesium silicate. Hardness is 2.5-4,
rarely 5. Fracture is conchoidal to splintery and the streak is
white. Colors are leek to dark green, yellow, and brownish. It has a
greasy luster and is often substituted for jade. How do you tell one
apart from the other in a bin of slabs at a rock show? It is very
difficult. I once bought a 12 square inch slab of the most beautiful
green rock with flower inclusions in it. I thought it was
translucent Wyoming USA flower jade. I paid $75.00 US for the slab.
If it was jade the cabs would sell for over $100 each in 15 carat
sizes. It turned out to be beautiful serpentine. Cabs worth about
$10.00 US each. Lesson learned.