What is black quartz

Quartz colors - natural and artificial colors of quartz

mineral Cause of color
agate Iron and manganese compounds
amethyst Iron oxides and manganese
Ametrine see amethyst and post-heating
Aventurine Inclusions of other minerals
Rock crystal -
Blue quartz Inclusions of rutile and crocidolite
Citrine Iron oxides and hydroxides and formation temperatures
Iron pebbles Iron oxides and hydroxides
Hawk Eye Inclusions of crocidolite
jasper Iron, manganese, chlorite, clay and loam
Carnelian Iron oxides and hydroxides
Milk quartz Inclusions of gases and liquids
onyx Iron and manganese
opal Structure of the mineral
Prasem Actinolite deposits
Prasiolite Formation temperatures
Smoky quartz radioactive radiation during formation
Rose quartz Titanium oxides and manganese
Tiger eye Inclusions of crocidolite

Color changes in quartz

The knowledge about the formation of quartz and the origin of the different colors is used for the subsequent change or improvement of the color. Sometimes the interventions are only minimal, e.g. to intensify the color or to correct the uneven color distribution in the mineral, in other cases a new color is created.

Burning quartz

Firing, i.e. the careful heating of minerals, is one of the oldest methods of changing or improving the color.

Naturally yellow citrine is the rarest member of the quartz family. In order to still be able to offer the mineral, purple amethyst is heated to 470 ° C, with the result that the former color changes and the citrine yellow is created. If you go to 500 ° C with the firing, the actual amethyst becomes a leek green prasiolite.

But “new minerals” are also created, such as mocha quartz, banana quartz, lily quartz, olive quartz, champagne quartz, strawberry quartz or cognac quartz, which give the impression of a special rarity, but none to date unknown varieties, but only artificially color-changed quartz crystals.

Irradiation of quartz

Another way to change the color of quartz is by radiation.

Electron and gamma radiation are used for this. According to the Federal Office for Radiation Protection, gemstones treated in this way are harmless. Smoky quartz, in particular, which is exposed to sources of natural radioactivity during its formation, is artificially produced in this way.

Coloring of minerals

Agates in bright pink, bright violet or bright blue are not a freak of nature, but the result of a color treatment.

The fact that agates can absorb color is explained by the mineral's porosity. The quartz variety is literally inoculated with color. Red is caused by iron oxides and hydroxides or iron nitrate solution, divalent iron, potassium ferrocyanide and iron vitriol color blue, chromium salt solutions in combination with divalent iron and heat cause a green color and black agates are the result of a color mixture consisting of carbon, sugar solution and sulfuric acid.

Sheathing or coating of quartz

A relatively new method of color change is the coating of minerals.

Quartz crystals shimmering in the colors of the rainbow are not a new discovery, but the result of laboratory work.
A popular example is rainbow quartz (other trade names: Aqua Aura, rainbow rock crystal) - a mineral that does not naturally exist among the more than 5300 minerals known worldwide. For this purpose, the quartz is vaporized on the surface with gold. A thin layer is created on the mineral, which creates metallic, colored effects. In professional circles, this process is called PVD, physical vapor deposition, known. In all cases, a fine layer of gold or titanium ions is vapor-deposited onto the mineral, creating new colors.

The new minerals that are created by PVD are, in addition to the rainbow rock crystal, moonlight quartz, blueberry quartz or golden quartz.

Disadvantages of the color treatment

The color of most color treated quartz is not constant. Just like naturally colored quartz, the color will fade over time if the mineral is exposed to frequent sunlight. It is therefore recommended that gemstone jewelry be stored away from light after wearing, for example in a jewelry cabinet or jewelry box.

A major disadvantage of PVD-refined quartz is that the mineral remains after the treatment is completed cannot be changed in shape. A burned, inoculated or irradiated quartz, the color of which has arisen afterwards, can be given a different cut at any time. The color is evenly distributed in the mineral. The PVD process, on the other hand, only applies a superficial, thin layer to a mineral. This can peel off and if the mineral is sanded, the PVD layer is lost. For this reason, the shape of the stone is determined before the stone is shaped.

Quartz - our recommendation *

Also interesting:
- Differentiate between calcite and quartz
- The agates from Idar-Oberstein
- hydro quartz

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⇒ Bauer, J .; Tvrz, F. (1993): The Cosmos Mineral Guide. Minerals rocks precious stones. An identification book with 576 color photos. Gondrom Verlag GmbH Bindlach
⇒ Korbel, P .; Novak, M. and W. Horwath (2002): Mineralien Enzyklopädie, Dörfler Verlag
⇒ Medenbach, O .; Sussieck-Fornefeld, C .; Steinbach, G. (1996): Steinbach's natural guide minerals. 223 species descriptions, 362 color photos, 250 drawings and 30 pages of identification tables. Mosaik Verlag Munich
⇒ Schumann, W. (1992): Precious and precious stones: all precious and precious stones in the world; 1500 unique pieces. BLV determination book, BLV Verlagsgesellschaft mbH Munich
⇒ Schumann, W. (1991): Minerals rocks - characteristics, occurrence and use. FSVO nature guide. BLV Verlagsgesellschaft mbH Munich
- www.bfs.de - Are gemstones radioactive?

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Last updated: March 2, 2021