Serpentine, Jade, and Olivine

Jewelry Discussion
1

Continue from:
New Colors in Jade?

Serpentine is indeed olivine, and good olivine/serpentine can be
translucent and have a 'ring' like jade but is much softer.  It
can be scratched with a pocket knife and even carved with good
files, yet it can also take a good polish using tin oxide on
leather at about 600rpm.  There is a deposit just on the edge of
Nelson city that used to be quarried and crushed for use on
agricultural land deficient in magnesium, and used to be used in
road making too.

I don’t think so, John. There is a high-grade rather hard variety of
serpentine called bowenite, that is translucent and makes a pretty
good substitute for jade, but it’s not as hard as olivine; it tops
out at 5.5 on the mohs scale (which is harder than most knives,
although files are harder). See

http://www.emporia.edu/earthsci/amber/go340/gb4.htm

In its crystal form, olivine is known to jewelers as peridot, which
is 6.5 to 7 on the mohs scale - a knife won’t scratch it. It makes a
nice clear green gemstone, and is hard enough to facet and set in a
ring. Jade (nephrite and the harder jadite) falls in between these
two in hardness. For more info on olivine/peridot see

http://ist-socrates.berkeley.edu/~eps2/wisc/oLect14.html

Olivine sand is hard enough to be commonly used for abrasive
blasting; most serpentine is quite soft; this depends on the
proportion of its two basic constituents.

Andrew Werby
www.unitedartworks.com

2

G’day;

I’d like to ‘rephrase’ my previous pontification on these
materials., having thoroughly checked now.

Firstly peridote is the crystal/gem grade of olivine. Serpentine is
altered olivine,

Bowenite is serpentine, but much harder, more translucent and has
different RI.

Anecdote: A Colleague of mine was doing research in Antarctica at
the base of mount Erebus. He’d done what he had come for, had packed
his gear and was waiting for the helicopter to take him back to base.
He was idly kicking stones (as you do), picked one up and found it to
be gem grade peridote, and collected about 500 grams in ten minutes!
On his return to NZ he showed them to me and gave me a nice bright
yellow one. I had it cut and mounted it in a 14 carat gold ring (all
I could afford) and gave it to Jean. She much later gave it to our
grandaughter.

Cheers for now,
JohnB of Mapua, Nelson NZ