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Questions about light


Thank you for your words of warning, it sounds like you know how
things work here, I hope you didn’t get ripped of…

Here is my question.

I have a laser pointer , similar to the type of laser that one
would put on the end of a firearm to increase accuracy, it has a
red laser light which is strong enough to penetrate almost any
colored stone.

Over the last few weeks I have been learning an incredible
amount about raw colored stones on the net , and have actually
been able to start identifying them when they have been brought
to me , i.e. taumanline(blue green ) , aquamarine , amethyst ,
garnets , and even some emeralds (poor quality albeit).

I have been using this laser light to check the stones quality ,
by this I mean cracks and fissures that they may have and in
every case the light has penetrated ( obviously where the stone
is not that badly cracked or rough) right through to the other
side so that I can see the light exit , as red.

this has proved to be the case with the taumaline , amethyst ,
garnets and aquamarine , that is until today.

I was brought a stone , brilliant green in color , about 3.5
grams (amazing color , I have to add) which I was informed was
an emerald , I had a look and by my limited experience I would
say that it defiantly is an emerald , when exposed to white
light , on the flat surface of a very bright torch , even
thought the stone is raw , you can see clearly through one half
of the stone , I would estimate about a full carat , possibly
more , absolutely crystal clear , yet when I shine the red laser
light on to the stone , it does not penetrate the stone , it
does not shine through or even shine onto the cracks on the back
side of the stone …like it would on the other stones
that I have applied this method too…?

I wonder if you could shed some light?..pun


I bought the stone , just out of fascination as it is really
nice , so dont worry , I paid next to nothing, but I would like
to know if you have had any other queries about red light and

kind regards
Greg Efendakis
Fendakis Investments
Zambia Limited

    his has proved to be the case with the taumaline [do you
mean  "tourmaline? ??" ] , amethyst ,garnets and
aquamarine , that is until today.   I was brought a stone
, brilliant green in color , about 3.5 yet when I shine the red
laser light on to the stone , it does not penetrate the stone 
I wonder if you could shed some light?.............pun
intended......*grin*. >> 

Greg - You can no more expect a green stone to transmit a red
light than you can expect the Grinch to sing Christmas Carols -
something about physics and wavelengths, I believe. Mike


This can permanently damage your eyes. Instead of this–use a
fiberoptic light source for viewing the internal structure.
Each time this laser light “flashes” in your eyes, a very small
bit of your retina is permanently damaged. Over a period of
time, the damage could be massive. I am a little rusty on optics,
rules of subtraction, etc, however I think that since you have a
green trasparent medium, red is filtered out and this is why you
see black–but it has to do with specific wavelengths and not
all red/green combinations are this way. Al Gilbertson


G’day Greg; The light from a ruby laser contains only red and
blue light. This is one of the test to differentiate ruby from
other red materials; even a simple spectroscope shows it up at
once. And Emerald reflects and transmits mainly green light. So
the red laser light gets completely absorbed and won’t be
transmitted by emeralds. Sorry about that.

Ref that pun; During WW2 I was in the Royal Navy and
thought it amusing to constantly pun at the slightest
opportunity. I was threatened to be thrown over the side in
Valletta Harbour - full of sewage in those days! A ghastly fate!
Before they’d let me go I had to repeat three times loudly, “For
every puny pun I shed I will be severely pun-i-shed.” (whisper -
it didn’t really cure me!) – John Burgess


Yes; the emerald would filter out all wavelengths except its
own green wavelengths. And since the red laser contains none of
these green wavelengths you end up with black. You need to use a
light with a more complete spectrum (including those green
wavelengths) if you want it to penetrate through the emerald.



Chromium in the emerald absorbes most of the red light emitted by
excited chromium in the LASER. If you focus a strong beam of
white light through a synthetic emerald, RED light emerges! Hold
up a bottle full of green Creme De Menthe to a strong light and
be amazed that it’s color is now red. More if you want…
Will Estavillo,