Green quartz crystals

We all know very well that there are various types of quartz crystals, but when it comes to the variety of green quartz crystals, and especially when considering them in connection with green amethyst, a slight confusion might enter the scene.

There are over 4000 known minerals today. If we consider all them, we will soon find out that there are over 800 crystals of green color... That is a huge number, and hardly there is a person who can distinguish them all. We have been considering the most important green crystals here, but there are many, many more. Even if we limit ourselves to just considering the quartz family of stones, there are a lot of stones... Let us see what we can learn from the quartz sub-classes of silicate minerals.

When talking about Quartz (Silica), there is one thing we should always have in mind. There are two large subgroups here...

1. One of them contains all the silica minerals whose crystals are macroscopic, that is, visible with naked eye. This sub-group is often called macrocrystalline quartz. Observe the word MACRO here. The members of this group all have large crystal grains, are mostly transparent specimens, with well defined form, often possessing prismatic elongated shapes with terminations at least on one side. Even if their shapes are not so regular, for example if we talk about tumbled stones, you cannot overlook their transparency, optical properties and visual appeal. In this group we can classify the following semi precious stones: rock crystal, amethyst, citrine, smoky quartz, rutilated quartz, etc...
2.  The second sub group contains all the silica minerals whose crystal grains are not directly visible. In some of them, not visible even under the microscope with large magnification. This is the group of microcrystalline or cryptocrystalline quartz. Observe the word MICRO here. Also you also can take a note of the world crypto, which means cryptic or hidden to address the unknown microscopic structure of the minerals therein (since for a long period of time it used to be a sort of a mystery). Here we can find silica minerals such as agate, jasper, chrysoprase, flint, onyx, aventurine, carnelian, chalcedony, ... etc.. Now, this group can be further divided, but I will stop here, and explain where I am going with this...

The above division comes handy when trying to classify the green quartz crystals. Strictly speaking, prasiolite green amethyst... or vermarine ... is the name reserved in mineralogy to any sort of green colored MACROCRYSTALLINE quartz. In this fashion, green amethyst also a macroscopic variety obtained from amethyst by heat treatment. For most practical purposes we can put the equality sign between the two: prasiolite = green amethyst.

On the other side, we have chrysoprase as a green variety MICROCRYSTALLINE quartz. This stone is not transparent, so there is no danger of confusing it with green amethyst. Here is a photo of one of the chrysoprase stones from my collection. (You can read about the other important green amethyst facts here.)

Chrysoprase- green microcrystalline quartz

Indeed it looks quite different. Chrysoprase is a form of fibrous quartz containing small quantities of nickel. In this case the microscopic crystal grains -- crystallites -- are distributed in a linear fashion so that they form invisible fibers. We can think of some other green silica stones: for instance, prasem quartz, or alternatively "emerald silica stone". Prasem possesses a deep rich green color of jade, with some beautiful specimens called imperial prasem.

Prasem stone

We should also mention aventurine. Aventurine is a mixture of two minerals, quartz and plagioclase feldspar with some addition of hematite, but as a rule it is always considered a variety of cryptocrystalline green quartz. Aventurine is sometimes confused with jade, and jade is a different class of silicate materials altogether.

Aventurine

Here we could also include green agate and green jasper, but in principle any form of cryptocrystalline quartz is far from being a match to green amethyst prasiolite, at least when it comes to the superior properties of the latter gemstone for jewelry production.

I hope we were able to learn a few things:

• that green amethyst prasiolite is a form of macro crystalline quartz crystal, like rock crystal  
• that there are much more forms of micro crystalline green quartz stones, like those presented in the photos above
• the micro crystalline green quartz stones are no match to prasiolite when it comes to their optical properties appreciated so much these days in modern jewelry design.