#22 - Crystal Growth

Posted on Thursday, September 13th, 2018 at 7:43 pm by LaLonde

Crystals are the basis for gems. Gems are all cut out of crystals that grow in the ground. Usually, these crystals form in molten pegmatite dikes, which form in the final stage of the magma’s crystallization. These are offshoots of thin layers of magma that branch out from the main channel of magma that creates the explosive volcano. As these dikes cool, the like atoms attack each other in layers and form crystals. Many gemstones are formed this way. As the crystals are forming, any disruption in the process causes flaws in the growth.

In my class at GIA, my teacher explained how ice cubes grow just like crystals – they grow in the hexagonal system. If you live in an apartment close to a busy road, when trucks drive by and shake your building, it can cause ripple effects in the growth of the ice cubes.

Now, think of the slopes of a volcano and the forceful eruptions and earthquakes and how it could affect the purity or durability of a crystal growth. Also, as the magma cools different impurities creep into the crystal zone which then cause impurities in the crystal. It’s a wonder how some crystals can form so cleanly and perfectly.

Green/White/Grey Panjshir Valley Emerald Crystal Specimen
Emerald crystal growth in marble. Emerald shows unique characteristic of a bend in growth.
This is indicative of a major earthquake causing the crystal grown to change direction.
Purchase this specimen here:


As these crystals grow, one of the 118 chemical elements can creep into the crystal. If a pegmatite dike cools and a number of crystals form, and then the geological powers form more magma that creeps in to the dike, it will cause everything to become molten again and then cool a second time. This time, different crystals can form – before where there was aquamarine and chromium creeped into the area, it may now become emerald! Chromium makes gems green, iron makes them blue, and nitrogen makes them yellow and so on.

This is why the right amount of an element is so important to the color of a crystal. Nature is so wonderful! All of these things have to happen deep in the ground over millennia.

When I have someone bring me an emerald that is beautiful in color with no flaws and sparkles like crazy, I really don’t have a lot to go on except to ask questions. Questions like “how did you acquire this? How much did you pay?  Where was it purchased? Usually I get the response “you’re the gemologist, YOU figure it out!” Sometimes, I remind them when you go to the doctor and tell him you are sick, do you tell the doctor “You figure it out!” No, you tell him what hurts and where it hurts, otherwise you can’t make a diagnosis!

One time a woman brought me a clean, top color emerald and made the statement that she has paid a lot of money for the gem. Well, I was sweating bullets because I knew it was a synthetic emerald. I wasn’t sure what to say. I thought and thought and finally I asked, “What did you pay?” She said “$300!”  What a relief! I thought for sure she was going to say $30,000.

I have realized, what seems like a lot to some, may not be so much to another.

Written by Daniel J. LaLonde

© LaLonde Jewelers 2018