Amethysts

Rubric "Minerals"

** All pyruvate! **

It would seem that this mineral is the most recognizable. Purple means amethyst, but it's not so simple.

** Amethyst is silica, a kind of quartz. Color is due to the presence of iron ions in the composition, although it was previously believed that this is a merit of manganese. At high temperatures, the mineral becomes, eventually, discolored. **

The color depends on the deposit. The most famous deposits are Brazil and Russia (Middle Urals). Brazilian pebbles have a rich purple color, turning into black. The Urals are paler, sometimes only the peaks of crystals are colored.

** A specimen of the Ural amethyst is a crystalline druza: several intergrown crystals on a common basis. A copy of the Brazilian amethyst is a crystal brush: a lot of small crystals, relatively evenly spaced on the substrate. **

Daylight

** Amethysts grow in agate geodes, as can be recognized from the substrate of the second sample: **

** Amethysts are characterized by pleochroism (not pronounced): in different lighting, they both slightly change color. **

Amethyst has a hardness of "7" on the Mohs scale. What does it say? In general, the scale classifies minerals at two extremes: the mineral or mineral scratches itself. Overstepping the hardness of "5" (and only 10 of them), minerals begin to scratch themselves. Therefore, the amethyst is hard enough, it scratches the glass, it can be processed with diamond.

** If you look inside the crystals, you can see a lot of interesting things: they are not homogeneous, transparency varies. **

The upper small crystal is transparent, since it contains only a few gas inclusions. For a larger crystal, only the peak is transparent, then a mass of inclusions is present. Sometimes they are not located chaotically, but rather organized (planes). In the sample, it is exactly this phenomenon, which, unfortunately, does not show up because of the low sensitivity of the camera. By the way, planes in minerals are sometimes called "curtains." Once, when I once again went to the bench with stones, a conversation started with the seller.

** He took a sample of rock crystal and said: "What curtains!" I glanced at the window and thought that, in general, it is strange to talk about curtains, because they were not at the window at all. Only a couple of days later I realized what " curtains " I was talking about. **

Curtains of amethyst

** Talk about the transparency of Brazilian amethyst is difficult due to the dark color. But in general, the situation is similar: transparency is uneven, inclusions occur, as well as internal cracks, reliefs. **

** The more correct the form of the trigonal crystal, the higher its value. Let's look at the peaks. Ideally, they should not be broken. **

** The sample, apparently, does not differ in special quality: the smaller peak contains a dent, as well as the larger one. **

** The Brazilian sample, on the contrary, is of high quality. The peaks of all the crystals are sharp, without fractures.
So what is the difference between the Ural amethyst and the Brazilian one? **

** Mineral aggregates are not distinctive features, like hardness, inclusions and quality. One thing remains: coloring. The vast majority of Ural amethysts are light, the Brazilian ones are dark. **

** However, it also happens that the color is similar. Therefore, it is necessary to acquire minerals alive, from mining specialists or those who know exactly where the sample came from. **

See you in the next posts.

** The photos are taken from the personal archive of the author **