How to distinguish amethyst from tanzanite?

Here you will find a continuation of the article about the similarities and differences between two beautiful gemstones – tanzanite and amethyst.

What do they look like?

Externally, both stones have a blue-violet color. There is little overlap here, however, as amethyst typically has red or pink hues instead of blue, and “good” tanzanite tends to be light blue to almost sapphire in color.

Both stones also belong to the silicate class, although the structure of tanzanite is much more complex. Tanzanite and amethyst also share pleochroism, or the presence of multiple colors depending on the angle of view. However, most amethysts are dichroic and have only two colors, while one of the defining features of tanzanite is trichroism. Finally, both stones are often heat treated. However, heat treating amethyst produces citrine (which makes up the bulk of commercially available citrine), and tanzanite is typically heated to give it its characteristic blue-violet color. Both stones are generally free of inclusions, and you will receive a large discount if the cut stone is not considered clean.

What is the difference?

These stones have quite different colors, especially when it comes to stones with a higher degree of coloration. The best tanzanites are almost the same color as sapphire and have a characteristic trichroism, while the most desirable amethysts have a grape juice purple color and red undertones.

The structures of these minerals are very different. The silica that makes up amethyst is a very simple molecule, arranged into a simple structure, while tanzanite is much more complex and contains many different elements.

Both stones form prisms, but amethyst has the characteristic hexagonal shape that is associated with quartz, while tanzanite tends to form into a tetrahedral rectangular prism. The latter also has more pronounced banding than amethyst. Tanzanite is also softer than amethyst, although overall it appears to be a slightly harder mineral when it comes time to set. After all, they are very different stones, and spending some time getting to know the colors is often enough to tell them apart. Tanzanite is much more easily confused with iolite or sapphire than with amethyst.

Questions and answers on amethyst and tanzanite

Is there fake tanzanite?

As with any expensive and rare gemstone, there are many fakes. If a deal looks too good to be true. it probably is.

Most counterfeits can be detected using a calcite dichroscope as they are usually made from non-pleochroic substances such as cubic zirconia or synthetic yttrium aluminum garnet. Forsterite is sometimes passed off as tanzanite and is a little more difficult to detect, but through a loupe it will show doubling of the pavilion facets when viewed through the crown.

Are there other types of treatments for tanzanite?

Some unscrupulous dealers sell stones coated with cobalt. This deepens the color of the tanzanite, but the coating tends to wear off over time, revealing the stone to be of a lower grade. This can be detected using a gemological microscope and even a magnifying glass. The latter, however, is likely to be difficult for an amateur.

What color of amethyst is most preferable?

Amethyst from the Ural Mountains is considered the best. It is a deep purple color that retains good transparency and red undertones when it shimmers in the light.

Is it possible to buy untreated tanzanite?

Currently, the Tanzanian government only allows very small pieces of tanzanite crystals to be sold outside the country. There is some material mined before the 2010 law, but it is extremely rare and the price per carat is usually comparable to that of cut stones.

Most of the “tanzanite” material sold is actually iolite, which is slightly harder but has a similar coloration. The easiest way to determine this is with a hardness test: tanzanite will not scratch a piece of quartz, but iolite generally will.

How do these stones look in jewelry?

Both stones are best reserved for special occasions as hand jewelry, but are great for everyday wear in necklaces and earrings.

Can tanzanite or amethyst be cleaned with soapy water?

Undoubtedly. Being silicate minerals, both tanzanite and amethyst can be easily cleaned with water without any problems. However, if you have exceptionally hard tap water, it is better to use distilled water to avoid calcium deposits affecting the clarity of the stone.

What causes the blue-violet color of tanzanite?

The coloring substance of tanzanite is vanadium. It also causes tanzanite to change color when heated. Its scarcity is one of the reasons that tanzanite is only found in one small region. Although they are very different stones, it can sometimes be difficult for a gem lover to tell the difference between tanzanite and amethyst. But you need to be able to tell them apart, and ultimately it’s a good idea to learn as much as you can about gemstones. So let’s take a look at amethyst and tanzanite and then share some interesting facts about these two stones!

What is amethyst?

Amethyst is a purple variety of macrocrystalline silica, also known as quartz. It comes in a variety of shades, from pale mauve to the deep purple associated with the Urals in Siberia. It was once one of the classic gemstones, but after the discovery of large deposits in North and South America, it was classified as semi-precious. In many cases, amethyst is relatively pure quartz. The difference is that in many places on the crystal lattice, iron has replaced silicon. When combined with moderate heat during formation, it becomes purple in color. The composition of amethyst is almost identical to citrine, it’s just that citrine was formed at a higher temperature when it was still underground. Amethyst is a fairly hard stone, with a Mohs hardness rating of 7,0. This allows it to be used in jewelry ranging from rings to bracelets, although it is not as durable as stones from the beryl (e.g., emerald, morganite) or corundum (e.g., sapphire, ruby) family. Amethyst can sometimes be difficult to set as it breaks relatively easily compared to more durable minerals. Amethyst is found in geodes, clusters and points depending on the region where it comes from. It is often found together with other varieties of quartz such as smoky quartz and clear quartz. Amethyst specimens are beautiful and relatively cheap. In particular, those looking for large specimens should look to the basalt deposits of Brazil, where this material is found in huge quantities. They are available almost anywhere you can find stones for sale.

What is tanzanite?

Tanzanite is a specific variety of the mineral zoisite. It belongs to the epidote group of minerals and is classified as calcium aluminum silicate. This strange species is found only in one very small place in the world. Specifically, tanzanite comes from the Manyara region of Tanzania. The first tsavorite garnets were found in the same area. Tanzanite is an amazing gemstone by any standard. It usually occurs as a brown crystal with blue and purple hues. It is one of the best examples of trichroism, which means it shows three different colors depending on how light enters the crystal. However, it is famous for its deep blue-violet color. This is due to heat treatment. Tanzanite is widely heat treated, although some gem-quality material has been discovered near the surface, which has sparked interest. It is believed to have been the result of a local event, possibly a large forest fire. Tanzanite is believed to have always been heat-treated, and gemologists say there is no way to determine whether the kiln or a natural heat source caused the color change. Tanzania made very good choices with this gem, including nationalizing the mines shortly after its discovery. Currently, the export of untreated tanzanite weighing more than 5 carats (1 gram) is prohibited, making these gemstones primarily a local treasure. This nationalization and several successful deals with large miners have led to tanzanite accounting for more than 7% of the country’s GDP. Cut tanzanites are relatively expensive, usually starting at $60 per carat and rising from there depending on the grade of the stone. Tanzanite scores 6,5 on the Mohs scale, so it is slightly softer than quartz. Despite this, the rich beauty of the stone has led to its use in all types of jewelry. Tanzanite rings and bracelets should be handled with care due to the softness of the stone, but they remain a favorite of many.