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Indian Geru, reddish mineral to add color?


I recently returned from a wonderful trip to India. While there I
had the incredible opportunity to visit the workshop of B.D. Sony and
watch them setting stones the Indian way and a few other processes.
Compared to our Western studios theirs was very primitive but the
work was absolutely incredible. One of the things that intrigued me
was they used a reddish mineral called Geru to add color to both
gold and silver. B.D. told me that it is sodium something but I never
heard the second word. I looked it up on Google Translate but no
luck. Can someone help? I would love to try it.

Thanks, Claudia in Texas



Is this the same B.D. that was at the Smithsonian Folk Life Festival
in Washington D.C. 2002? I was there demonstrating as well. I went to
Udaipur in 2007 and tried to locate him, but had no luck. He claimed
his father did Kundan work, but I learned this was not true when
Asking around.

I’ll ask a friend about the Geru.


One of the things that intrigued me was they used a reddish mineral
called Geru to add color to both gold and silver. 



I used to live in India many years ago and saw it used widely (geru)
its actually an iron oxide, or red ochre. It is used in painting and
metalsmithing. you can buy it at good art supply stores. I don’t
think its sodium anything…rer


In the 60’s polishing rouge was referred to as a polish and color
enhancer for gold and silver.

Tony Konrath

In the 60's polishing rouge was referred to as a polish and color
enhancer for gold and silver. 

Polishing traditionally divided in 3 distinct phases - buffing,
polishing proper, and coloring. Coloring does not mean changing color
of metal, but bringing natural metal colour forward.

From that point of view, red rouge is a coloring agent.

Reference to 60’s is interesting, because coloring is impossible on
cast objects, and it is 60’s when casting madness has began.

Leonid Surpin


Claudia- to clarify what I said and the responses about colouring
gold : Red ochre is widely available, it is a paint pigment
primarily but can be added in very small amounts to ALLOY a karated
gold. If you want to know the exact proportions so you don’t waste x
amount of casting grain or scrap write me off list and I’ll send you
recipes. Yellow ochre is another pigment used by artist and in
metalsmithing and as a stop flow in soldering-they are not the same
pigment. I got a couple of emails off list that led me to write this
regarding yellow ochre. Mixed to a paste ( heavy cream consistency
actually) it will stop the solder’s flow on metals to some degree and
washes off easily, and is less toxic than some “white-out” products
on the market when heated. The ochres are clays in essence- rouges
are grease suspensions of iron oxide polishing agents that enhance
the colour of metals in the final stage of polishing. NEVER add
rouges to an alloy, master alloy or scrap recalimation project. for
one thing the binders will separate out or evaporate in part, but
they are iron oxide based and will contaminate the precious metals,
the crucible and yield unpredictable results when you roll or draw
the alloy into a usable raw material. Whomever posted about rouge was
mistaken about the colouring you referred to. I have almost
eliminated using rouges on yellow golds with the introductionof 3M’s
radial bristle discs, tri-m-ite polishing papers and films and
diamond sanding bands…the discs give me great finishes after
pre-polishing when necessary (depending on the raw material I’m using
to begin the project: if i just rolled out wire or sizing stock it
needs little rouge anyway and the 6micron discs do a great job of
imparting a high shine if that’s what I’m after). So, i hope you
have found the geru and are experimenting with it in your studio in
1-2grams of 24 kt gold :. 25 gms-1. 75 gms silver, copper or a
combination of the two and adding no more than. 060 gms of geru per
2 gms gold regardless of what you are alloying with it. The geru
binds to the flux in non-graphite crucibles sometimes so make sure
your crucibles are red hot before adding metals…otherwise the red
ochre/geru may stick to the flux glass if added too soon and become
a useless step you have taken requiring sal ammoniac and charcoal to
try and pull it out of the alloy (a refining flux of 1part sal
ammoniac to 1 part of powdered activated or pure wood charcoal can be
used for any gold scrap reclaimation project to yield a brighter but
tougher ingot). I hope this clarifies everything for you.

to clarify what I said and the responses about colouring gold : Red
ochre is widely available, it is a paint pigment primarily but can
be added in very small amounts to ALLOY a karated gold. 

I am not going to deny that practice of adding red rouge/red ochre
does exist. But it is important to understand why it is done.

There is a technique employed by western goldsmiths to add a bit of
tools steel to silver melts. For the shop practice, it amount to
simply do not use magnet to remove iron fillings from scrap. Remove
large pieces like broken blades, binding wire, but do not bother with
fillings, unless there is a lot of it. As long as it is under 0.5
percent, it helps with casting of silver. I am not sure about the
gold alloys. For gold alloys I do recommend magnet treatment.

Practice of adding red rouge/red ochre to melts is another way of
introducing iron in alloy. Red gouge is iron oxide which converts to
iron at high temperature and presence of flux. It does improve
crystal structure of alloys and thereby improves alloy colour. So to
say that adding red rouge to alloy improve it’s colour is true and
misleading at the same time.

Leonid Surpin



as far as I’ve followed this subject, the advice is/was NOT to add
red rouge to an alloy but red ochre instead or am I wrong?.

Why adding red rouge in an alloy? It’s smells like hell and smoke
all over the place, great ! One could try by adding hematite to an
alloy wich is about the same composition.

Have fun and enjoy


Hello Pedro,

Though grinding hematite leaves everything red in the studio that
its dust touches (clean surfaces with alcohol, citrus oil or similar
solvents based wipes and re-oil tooling, and dispose of (or seal in a
bag) any sandpapers, films, etc. used (or beginning to clog though
still potentially usable) after cleaning (and remember to separate
them from recycling trash/sweeps/polishing cans before sending them
in to your refiner or attempting to melt and pour scrap) it is
definitely not the same thing as rouge or other iron oxide clays that
are being discussed as they are bound in a crystalline structure -
which makes hemetite a rock, with x degree of hardness and not
necesarily soluable even with the high heat involved in reclaiming
scrap or creating a karated gold (or silver) alloy.

the substance in question was red ochre, or “geru” as is used in
Indian metalsmithing (occasionally one finds it used in central
america as well). It is easily ground and incorporates fairly easily
into the crucible’s contents but is wholly inferior to ready made
master alloys or even combining your own metals and minerals ( such
as zinc, germanium, chromium, etc.) to yield different coloured
golds. Iron oxides are not all equal even though the same
terminology is used to refer to an iron containing mineral or rust,
and in many stages of refinement- rouge being more refined than
attempting to collect rust from tools and using it to slightly
enhance the colour of an alloy. Too much and it is a contaminant that
will yield very strange results in the rolling or drawing process…
a good scale is absolutely necessary when trying to use iron oxides
at all as measurements have to be precise.

As for recommending its use (geru) at all- I am definatively NOT
RECOMMENDING it whatsoever ;. the amount necessary to see a good
result as a colourant requires at least 6 grams of 24 karat grain to
being with. At the current price of gold, using even that amount of
grain isn’t worth the experiment in my opinion. You would get
predictably better results following a non-ferrous recipe for a
coloured alloy for a peach, red-orange, or orange gold if that’s what
you are after, or starting with a very yellow grain and not reducing
the karat below 18K to retain the rich colour of grain/raw material,
for example, of an African origin. geru is a traditional but outdated
method when nothing else is available and one is very skilled at its
use- or for those with an unlimited budget in this time; its use ws
begun when gold was less than 150.00 an ounce which seems cheap
these days but luxury cars only cost $3000.00 back then so its all
relative to economics. A few years ago in the 1990’s gold was still
only $265. 00 an ounce…far more easy to rationalise an experiment
with a half ounce of pure gold to begin with !.. rer


Hello Rourke,

thank you for all this and knowledge you wrote.

I’m not recommending anybody to use hematite at all, just a quick
thought concerning the iron oxide invalved in this matter.

I’m not dealing with this “geru-stuff” or hematite. It was just a
reaction which came up in my mind by thinking how someone is trying
to add red rouge in his melt… smoke, smell, nasty working
conditions etc I know that hematite has about the same consistency
and that’s why I made the comparison. Fact is that I don’t even have
any experience using this procedure of “coloring” or “staining” a
metal with these components. Going into trouble by grinding hematite
in order to collect the iron oxide is no option for me and I do not
wish to start with it. It is like you mentioned in your post, gold is
a way to expensive to monkey around with and the specification of the
new alloy are not worth it.

The red ochre deal is or might be something different but why using
this technique if their is no major benefit you can use? Other metals
are more reliable to work with and proven their excellent alloying

It’s nice of you that you corrected me this way, but I’ve never had
the intention to start with it, never want to give someone the
impression to use the hematite instead. My apology if someone
understood my previous posting about the hematite matter.

Have fun and enjoy


The method that was explained to me was to rub or paint a slurry of
Geru on the finished piece. Heat the piece gently and repeat.