Citrine has many forms, but not all of the stones called by this name are truly Citrine. Amethyst in disguise is only the tip of the iceberg!

First of all, let's start with what Citrine IS. Citrine is a variety of Quartz, Silicon Dioxide, that has yellow, yellowish green, or yellowish brown coloring. Citrine is found in locations all over the world but is considered rare in its natural form, as seen here.

The most common way that false Citrine is created, is to heat Amethyst at high temperatures until it turns orange. All bright and dark orange Citrine is in fact heated Amethyst. Below is an Amethyst geode that has been cut in half, with the right side heated to produce orange Citrine. The orange can range from bright to dark, brownish orange but always orange. True Citrine is never this color, although sometimes Amethyst is heated to orange naturally.

Genuine Citrine will always have yellow based coloring. It can be pale yellow, yellowish brown, yellowish green, bright yellow, or even yellowish orange like this Citrine:

It can sometimes be so similar to light Smoky Quartz that it is impossible to discern between the two, in which case either name is correct. This rare Smoky Citrine here is from the Congo and often called Kundalini Quartz. This coloring can also be referred to as "honey" Citrine.

This one has dark, smoky phantoms in yellow Citrine, cut and polished into a point:

These are also natural Citrines that have been cut and polished into points. These ones are from Brazil:

There are other instances where crystals are mistakenly called Citrine due to their color, even though they are completely natural.

One example is when clear Quartz is coated in iron oxides that are yellow or orange in color. These naturally occurring coatings can be opaque or translucent, but some people mistake the overall orange or yellow coloring for being Citrine.

Spirit Quartz is another crystal that I see being called Citrine quite a bit. These crystals feature a Quartz or Amethyst crystal that has a second generation of smaller Quartz or Amethyst crystals formed along the sides.

They occur as Amethyst, or white Quartz, but never actual Citrine, or Ametrine, though both often have some orange or gold colored iron oxidation. 

True Ametrine, the bicolor mix of Amethyst and Citrine, is very rare and only legitimately mined in Bolivia at the Anani Mine site. It is also called Bolivianite. Sometimes Amethyst has orange iron oxides in it and will appear similar to Ametrine, but you need to be very careful about location and identification.

This is a genuine, bicolored Ametrine from Bolivia that has been faceted for jewelry. 

So keep in mind that there is much more to Citrine than just the color of the stone! And maybe keep a real one in your pocket or on your desk if you're looking to make better money ;)

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There are so many different crystals and gemstones that exist in nature, and collectively they have an incredibly vast range of colors all over the spectrum. Some types of gemstones can have several different colors, like Topaz, Quartz or Tourmaline. So how do they get their colors?

In their chemical structure, gemstones have trace amounts of different transition metals either as part of their chemical compound or as impurities. Transition metals are the metals that make up the large, middle part of the Periodic Table, and these metals are able to absorb colored light. Different wavelengths of visible light can be absorbed by different transition metals, leading to the different colors that we see. 

Purple Amethyst - colored by the irradiation of Iron ions in place of Silicon

For example, the purple coloring of Quartz that we call Amethyst is caused by the irradiation of Iron ions in place of Silicon in some locations of the structure.

Garnet’s red coloring is caused by Iron ions replacing Magnesium ions, and the lovely blue variety of Beryl that we call Aquamarine is from the presence of Iron ions replacing Aluminum ones.

Citrine

Emerald

Opal

Quartz w/Hematite

The yellow color of Citrine - another form of Quartz- is caused by Aluminum or Iron impurities.

In Emerald, Chromium ions replacing Aluminum creates green. In Ruby it creates red!

Topaz in it’s pure form is colorless, while atomic level imperfections cause the blue, yellow and brown varieties. 

Topaz in it’s pure form is colorless, while atomic level imperfections cause the blue, yellow and brown varieties.

Transition metals are not the only way that gemstones get their colors, however. In some stones, such as Sapphires, it is caused by the transfer of electrons between ions.

 Color can also be caused when an ion in a specific place is missing within the structure, or diffraction of light through the structure, like in an Opal.  

Simple inclusions of tiny minerals inside a larger solid crystal can change its color. For example if a clear crystal like Quartz or Apophyllite or Calcite has red Hematite in it, the color of the crystal itself can appear to be red.

These are the most common reasons for the colors of crystals, or at least their colors as they appear to the human eye. There are more reasons, for more complicated crystals such as Alexandrite, Labradorite and some Fluorites. Crystals are complicated and the more you learn, the more complex they become!