Purple Gold

Jewelry Discussion
1

How in the ding dang do you make purple gold? I know (from
literature) that it is made from aluminum and 24k HOWEVER
everytime I try to mix it, it “freezes” up and after that happens
it is impossible (from my perspective) to remelt it without
totally ruining it. Parts of my “freeze dried” mess do have a
beautiful purple color . This is how I’ve been trying it:
in a brand new clean crucible, not using any flux I first heat
the aluminum gently (not concentrating the flame on the metal)
and when it starts to melt I add the gold but when the gold
starts to melt it just hits the aluminum and goes hard. I am
using an oxygen and acetylene torch. I have heard that purple
gold can’t be worked normally but does anyone know what CAN be
done with it? I have also on rare occasions seen blue, real nice
blue color gold, I believe it is alloyed with Iron and I’m pretty
sure that you would need some high tech equipment for that. But
for the moment I would like to at least get a nice mix on the
purple gold and whatever form it is I’m sure I can make something
with it, even if its just “sculpturing”. Thanks in advance.

Richard Laspada
Westtxn@worldnet.att.net

2

How in the ding dang do you make purple gold? I know (from
literature) that it is made from aluminum and 24k HOWEVER
everytime I try to mix it, it “freezes” up and after that happens
it is impossible (from my perspective) to remelt it without
totally ruining it. Parts of my “freeze dried” mess do have a
beautiful purple color . This is how I’ve been trying it:
in a brand new clean crucible, not using any flux I first heat
the aluminum gently (not concentrating the flame on the metal)
and when it starts to melt I add the gold but when the gold
starts to melt it just hits the aluminum and goes hard. I am
using an oxygen and acetylene torch. I have heard that purple
gold can’t be worked normally but does anyone know what CAN be
done with it? I have also on rare occasions seen blue, real nice
blue color gold, I believe it is alloyed with Iron and I’m pretty
sure that you would need some high tech equipment for that. But
for the moment I would like to at least get a nice mix on the
purple gold and whatever form it is I’m sure I can make something
with it, even if its just “sculpturing”. Thanks in advance.

Richard Laspada
Westtxn@worldnet.att.net

3

The aluminum has a lower melting point than the fine gold. Try
dissolving the aluminum into the melted gold. The mix is pretty
specific too- 18-19 karat 75-80% gold by weight. Acetylene has a
very high heat transfer rate, propane or natural gas would
probably be better for this alloy.

Rick Hamilton
Richard D. Hamilton, Jr
http://rick-hamilton.com
@rick_hamilton

4

Hi all,

Ok , there was this thread a while back about blue gold.

Anyway, There’s this company in South Africa, called Mintec. They
had an article a month or so ago in SA Jeweller, about a mix of
alimimium and fine gold-- to 18k.t-- and there was a picture of
it in facetted form.

I ordered it from them and they made me a button, about 10mm or
so in diameter. It is a nice colour, sort of looks like purple
Haematite. It’s got a sort of amythist-ish colour in incadecent
light, and a cooler colour in neon light .( my opinion) The
colour is pure all the way through.

It cost me ±R100/ gram.(16US) I carved it into a flower with an
emerald inlay. It drills with Tungsten-carbide bits, but as with
everything, diamond bits work best. I used Silicone rubber wheels
to finish up to rouge, and after it was rouged up it came to a
brilliant polish.

When you work it it can make small chips, so a soft touch is
wanted. The powder that comes off looks and feels like that
eyeshadow stuff that my girlfriend uses.

I didn’t heat it up, in fact, I treated like a Tourmaline, in
all aspects, since this was a brand new material for me, and
maybe it had inherited tourmalines Bad Moods, as they
sometimes have. It didn’t. It works like soft opal and from my
experience I would put it at ± 4 on the Mohs scale.

It is known as an intermetallic compound.? What’s that? I thought
that alliminium is a metal? How can something that is as soft as
aliminium or gold mix to become so hard that it blunts an
ordinary drill? Strange world!

Anyway For the record, I also ordered The Mysterious Blue Gold
.(Indium/Gold ) It’s not blue–I mean BLUE-- It’s the same as
green gold is not apple green. It’s green after a couple of
beers, yes, but not green.

Feel free to e-mail me for anthing you want to know

Cheers,
Hans.

5 
  Anyway For the record, I also ordered  The Mysterious Blue
Gold .(Indium/Gold ) It's not blue--I mean BLUE-- It's the
same as green gold is not apple green. It's green after a
couple of beers, yes, but not green.

Hans, I’ve seen a few pieces pictured where the “blue” gold used
was an intense lapis lazuli blue, similar to that obtained by
anodizing titanium or niobium. My understanding was that the
final color is obtained as a surface patina through chemical or
heat, rather than being an intrinsic color of the metal. However,
this is only conjecture, rather than something I’ve actually
done and held in my hand. Could your alloy also be one designed
for this type of treatment after being fashioned into it’s final
form and finish?

Peter Rowe

6

you have me curious…i’ve tried to make my own purple and blue
alloys, with limited sucess. what is the address of the company
that can supply these alloys? doug zaruba

7

I have read about purple gold. I was under the impression that
it is so brittle that it shatters if you drop it. Has anyone
had this experience with it?

8 
 It is known as an intermetallic compound.? What's that? I
thought that alliminium is a metal? How can something that is
as soft as aliminium or gold mix to become so hard that it
blunts an ordinary drill? Strange world!

most metals and alloys that we use crystalize as complex mixes
of usually cubic system crystals, composed of various pure metals
or solid solutions of pure metals, with the overall piece of
metal being a random mix of these various composition metal
crystals. The crystals themselves allow atoms to dislocate, or
slip, in several directions along planes of atoms within the
cubic structure, and the boundaries between crystals also allow
distortion without breaking. Thus the metals are soft, or
malleable, or ductile, etc. With intermetallic compounds, the
gold and the aluminum behave almost more like a chemical
compound than a solid solution mix. Not chemically, but in the
structure that forms. Neither gold nor aluminum is soluable in
the other to any significant degree, so they stay seperate. But
we’ve forced them to mix. What they form is a layered structure
of a layer of gold atoms, then a layer of aluminum ones, then
another of gold, etc. The resulting material has
characteristics wildly different from the parent materials by
themselves, neither of which is purple either. It does not have
a cubic system crystal structure, and the crystaline structure
formed does not allow the slip plane dislocations that our
familiar metals allow, thus the material is brittle instead of
being malliable and ductle.

By the way, this type of structure related brittleness is not
exclusive to metals which do not mix. gold and copper are
ordinarily somewhat intersoluable. Not completely, but somewhat,
and alloys normally form good workable metal. But an 18K alloy
of only gold and copper happens to have about a 1:1 ratio of
gold to copper atoms, and if this alloy is allowed to cool too
slowly, as it passes about the 700 F mark (I don’t recall the
exact point, and cant seem to locate my copy of the phase
diagram, so don’t ask me for more precise data. This is just
from memory), it it cools too slowly, the gold and copper can
also segregate out to a significant degree, also forming a
similar structured array of alternating layers of gold and
copper. This too, is quite brittle. If you’ve ever had an 18K
rose gold casting crack when dropped, or just break apart for no
apparent reason, then you have discovered this interesting
structure. It can be avoided either by including a bit of silver
in the alloy, so it’s not quite so red in color, or by being sure
that the alloy is never cooled slowly through that temperature
range. When you anneal or solder this alloy, you have to quench
it. Castings also must be quenched before the flask cools too
far… That done, the alloy retains fine working properties and
strength.

Peter Rowe

9

Hi Hans, Do you have the address where I might be able to get the
buttons of the purple gold. I am interested in cutting them into
color elements in my 18 kt and platinum jewelry.

Thanks, Etienne Perret

From: “Hans Meevis” afrigold@info.bw
Reply-To: orchid@ganoksin.com
Subject: [Orchid] Purple Gold
Date: Mon, 31 May 1999 19:06:44 -0500
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Hi all,

Ok , there was this thread a while back about blue gold.

Anyway, There's this company in South Africa, called Mintec. They
had an article a month or so ago  in SA Jeweller, about a mix of
alimimium and fine gold-- to 18k.t-- and there was a picture of
it in facetted form.

I ordered it from them and they made me a button, about 10mm or
so in diameter. It is a nice colour, sort of looks like purple
Haematite. It's got a sort of amythist-ish colour in incadecent
light, and a cooler colour in neon light .( my opinion) The
colour is pure all the way through.

It cost me +-R100/ gram.(16US) I carved it into a flower with an
emerald inlay. It drills with Tungsten-carbide bits, but as with
everything, diamond bits work best. I used Silicone rubber wheels
to finish up to rouge, and after it was rouged up it came to a
brilliant polish.

When you work it it can make small chips, so a soft touch is
wanted. The powder that comes off looks and feels like that
eyeshadow stuff that my girlfriend uses.

I didn't heat it up, in fact, I treated like a Tourmaline, in
all aspects, since this was a brand new material for me, and
maybe it had inherited  tourmalines  Bad Moods, as  they
sometimes have. It didn't.  It works like soft opal and from my
experience I would put it at +- 4 on the Mohs scale.

It is known as an intermetallic compound.? What's that? I thought
that alliminium is a metal? How can something that is as soft as
aliminium or gold mix to become so hard that it blunts an
ordinary drill? Strange world!

Anyway For the record, I also ordered  The Mysterious Blue Gold
.(Indium/Gold ) It's not blue--I mean BLUE-- It's the same as
green gold is not apple green. It's green after a couple of
beers, yes, but not green.

Feel free to e-mail me for anthing you want to know

Cheers,
Hans.

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10

Hi, I spent a lot of time trying to work with 18K purple gold.
The alloy is easy to make up; 1 dwt. of aluminum and 3 dwt of 24K
gold melted together. I rolled the 24K out thin and wrapped it
around the aluminum. It mixes easily and looks wonderful when it
cools. Then the fun ends. If you hit it with a hammer, it shatters. Tom Arnold

11

I found a reference for formulas for blue and purple gold that
were part of a table called, “Composition and physical properties
of alloys.” It was from the chemistry dept. at Dominguez Hills
College.The Purple gold formula was given as 79 AU, 21Al. I was
so intrigued by the description of the purple gold that I did try
weighing it out in 14 K as I did not have any 24K available (so
it had silver and copper in the alloy as well), and melting it
together in a spare crucible. The color was gorgeous, but it
had the texture of tuff, spongy glass, and crushed with a fair
amount of pressure. Needless to say that it went into the sweeps.
I may try again using 24K if this thread keeps my curiosity
going–I do some faceting, and had not considered that treatment
for the purple gold alloy previously. --Barbara Bequette

12

Hans: Does Mintec have a U.S. mailing adress? If not, please
post the South African adress as I would be very interested in
this material.

Thanks in advance;

Steve Klepinger

13

The formula given for BLUE GOLD in the “Composition and
physical properties of alloys” table is listed as 75Au 25Fe. I
have not tried this one out, perhaps John Burgess has more info
on this one. By the way, I always make copies of Mr… Burgess’
…thank you for sharing!
–Barbara Bequette

14 
     I spent a lot of time trying to work with 18K purple
gold. The alloy is easy to make up; 1 dwt. of aluminum and 3
dwt of 24K gold melted together. I rolled the 24K out thin and
wrapped it around the aluminum. It mixes easily and looks
wonderful when it cools. Then the fun ends. If you hit it with
a hammer, it shatters.

Hi Tom, At what point did you “quench” the alloyed metals… or
were they just air cooled… some metals work fine if they are
quenched at 700oF some when they are cherry red and some metals
are best left to air cool with no help at all.

The special sterling alloys that i use in casting need to be
quenched after 20 minutes,at this point the metal is nice and
ductile… if quenched after 5 or 6 minutes… the metal is so
brittle that it will crack when you put a ring on a ring mandrel
and attempt to stretch it. Reheating the rings to a dull red and
allowing them to air cool returns the ductility. Perhaps some of
these “anealing” tricks can be used on this special purple gold
alloy. Just my 2 cents. Visit the workshop at
http://www.racecarjewelry.com Daniel Grandi

15

Dear Peter, Wher do you find all this techno info? Are you a
meteralist also?You’ll have to excuse my given statements about
acids & cyanides. I almost killed myself once back in the late
70s using an acid/cyanide antiquing compound. I know they don’t
usually mix the two, by I was into finding the perfect antique
that would’t come off anything under any situation of wear,
tear, age or manufacturing. I found this compound called Jet
black or something like that. It’s been so long I can’t remember
the exact name. The stuff was so toxic I haven’t seen it in many
years. But you burned it on. Even with exhaust vents blowing the
stuff knocked me out. I was sick for several days. Since then I
have tried to rid my shop as well as our program here in
Minnesotaof all acids, cyanides & asbestos. My coments have been
more of safety concern than any expertise on their usage. The
only stuff we keep around are premixed plating solutions and a
small amount of nitric acid for gold testing. I would be very
interested in seeing some of your work. Do you have it posted any
where? One of my rings should be in the gallery section shortly.
With great respect, TR the Teacher

16

Hi Doug, The address for the company that makes purple gold is
elmavdl@mintek.co.za Cheers, Hans

17

Hello Barbara, If you try the blue gold alloy, Try warming it
slightly. At about 300F, you will find that it turns black. Very
pretty and I have absolutely no idea why. Have fun. Tom Arnold

18

Hi Peter! Your instructions about purple gold and red gold are
very interesting. You are obviously well versed. I would like to
know more about what goes on in the flask, and with the alloys-
metallurgy. I have unfortunatly a very elementary science
backround. Could you recommend some easy reading so that I can
gain a better understanding of my materials? Any help you can
through my way is greatly appreciated- as are your regular
contributions-Thanks!!! Rona

19

As a student in metalsmithing and jewelery design, I am indebted
to the knowledge that abounds here! The info on purple gold is
valued as ‘exotic’ colors of gold is where I want to go in my
career. Where were you guys when I needed this while writing a
research paper on this and blue gold? :slight_smile: Question…Any
resources out there on the blue gold? I know I can count one you
folks for the info. Thanks in advance, J. Shaw

20

I saw a thread on here from June of 1999 on purple gold and I
thought you might enjoy this:

http://www.gold.org/pub_archive/pdf/SpecialColoursUpdated2006.pdf