What scientific applications do sapphires have

sapphire

Author: Torsten Purle (steine-und-minerale.de) | Last update: 04/27/2021


Sapphire - properties, formation and use

english: sapphire | French: sapphire


Sapphire = blue corundum

Sapphire - the name says it all. Sappheiros is derived from the Greek with blue translated.
For a long time, well into the Middle Ages, almost every blue mineral or rock was called sapphire because of its blue color alone, even if it was other minerals or rocks such as lapis lazuli.



Table of contents sapphire


Properties of sapphire

The mineral sapphire has the chemical composition Al2O3 counted to the class of oxide minerals. Together with red ruby ​​and colorless leuco sapphire, sapphires form the corundum group.

Sapphires crystallize following the trigonal crystal system and form tabular, pyramidal and rhombohedral crystals. The corresponding aggregates appear grainy or bulky.

Sapphires show no cleavage, the fracture of the mineral is splintery and shell-like. The transparency of sapphire is see-through to translucent. The shine is glass-like or diamond-like, sometimes also silky due to minerals such as fine rutile needles embedded in the crystal. Those inclusions also cause the so-called Asterism of sapphiresthat take the form of a six-pointed star express. The reason: rutile needles that have grown into the sapphire and that cross each other and are sold as Star sapphire sold.

Sapphires have a Mohs hardness of 9 on the 10-point scale of the hardness of minerals according to the German mineralogist Carl Friedrich Christian Mohs (1773 to 1839) very hard mineralsthat meet the gemstone hardness criterion. Not every mineral is a gem at the same time. Only minerals with a Mohs hardness higher than 7 are defined as gemstones. The density of sapphire is 3.9 to 4.1 g / cm3.


Saphir - Our recommendations *

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The color of sapphire

The color of sapphires is not exclusively blue.

Even if the majority of all sapphires unearthed are blue in color, the corundum mineral also comes in colorless, black, red-violet, green, yellow and orange under the name Fancy Saphire.

In many cases, the color of sapphires or the shade of blue provides information about where they were found.

Location colour
Thailand green Blue
Montana / USA light to gray blue
Kashmir / India cornflower blue
Sri Lanka light blue, purple, yellow, colorless, green, pink
Australia dark blue to black, yellow green

Due to the similarity in color, blue sapphires can be confused with zircon, cordierite, kyanite, spinel, tourmaline, topaz and tanzanite.

Pink sapphires are also called sapphires labeled - despite the similarity in color to rubies. The decisive factor is the base color, which is red for rubies, while pink or pink dominates with pink corundum.
The fact that pink sapphires are counted as sapphires is based on the value of the gemstones. The color red is the most important quality characteristic of rubies. Rubies in a pronounced pink would be rated as stones of poor color quality and accordingly less valuable.

In order to avoid confusion with other colored minerals and gemstones or to point out that sapphires do not only exist in the familiar blue color, the color is also mentioned in the name of other colored sapphires for identification, e.g. Pink sapphire.

The coloring elements that are the cause of the typical sapphire blue are Titanium and iron.
With a comparatively low iron content, sapphire is green or orange. In contrast, vanadium colors sapphires purple.

Despite the many different colors, the line color of all sapphires is white, i.e. if sapphire is painted over an unglazed porcelain tablet (so-called streak board), a white powdered abrasion is created.


Origin and distribution of sapphire

Sapphires come from both igneous and metamorphic conditions (for details see: Formation of minerals.
Sapphire of igneous origin emerges from silicate rock melts of igneous rocks.
The prerequisite for metamorphically formed sapphires are aluminum-rich parent rocks, which are melted and then recrystallized as a result of high temperatures and high pressure, for example in tectonic or mountain-forming processes.

Sapphires are characterized by their high resistance to weathering, i.e. sapphire is particularly resistant to the effects of chemical and / or physical decomposition. That is why sapphires are often deposited in the form of soaps - after previous weathering of the sapphire-containing bedrock. In geology, soaps are understood as the accumulation of minerals in sand or other loose sediments.

In addition to garnet and ruby, zircon and spinel are the most common accompanying minerals of sapphire.

There are significant deposits of sapphire in Norway; Finland; Scotland; Ireland; England; France; Eifel / Germany; Ticino / Switzerland; Greece; Slovakia; Russia; Kenya; Malawi; Tanzania; Mozambique; South Africa; Madagascar; Afghanistan; Pakistan; India; Sri Lanka; Burma; Cambodia; China; Australia; New Zealand as well as in the USA.


Trade names and other names of sapphires

In the trade, sapphires are sometimes added to the name of the origin, and other minerals that are not sapphires are issued as sapphires.
The idea behind these so-called trade names is to give a mineral with a lower value an apparently more valuable image, e.g. cordierite, which is known as water sapphire.

Uses and meaning of sapphire

Sapphires are among the most important industrial minerals in the world.
The blue gemstone is not only used as a stone for jewelry; Sapphires are also used as a stabilizer in clocks and many electrical precision devices. Due to its infrared and UV permeability, the mineral is also used in optical devices such as lasers or LED lights.

The porcelain industry sometimes uses powdered sapphire together with silicates to make refractory ceramics.
The industry has long made use of the hardness of artificially produced sapphire crystals. Synthetic sapphire glass is used primarily for watches to protect the watch glass from scratches, but also to protect the displays of smartphones to equip scratch- and shock-resistant screens made of synthetic sapphire.


Famous sapphires

Many well-known and historic sapphires can be found in the collections of the American Museum of Natural History in New York / USA, such as "Star of India", the world's largest cut star sapphire at 536.35 carats.
The largest oval cut star sapphire bears the name Star of Adam. Almost the size of the palm of your hand, the star sapphire weighs 1404.49 carats on the fine scale, which corresponds to a weight of 280.89 grams.


Sapphire and jewelry

Sapphires, rubies, emeralds and diamonds have been the classic colored gemstones in the jewelry industry for centuries. The four large gemstones have always been made into jewelry and their popularity continues.

Depending on the purity, both facet and smooth cuts are used for sapphires. Cloudy sapphires or star sapphires are preferably made into cabochons, tumbled stones or donuts.

Crystal clear sapphireswhose focus is on purity, color and the color nuances resulting from play in the light Facet cut Mistake. The following cuts are particularly common in sapphires: antique cut, oval cut, pear cut, hexagonal cut, octagon cut, brilliant cut, heart cut, princess cut, navette / marquise cut, briolette, square cut, round cut, emerald cut, pillow cut or Asscherschliff.

For a long time, sapphires were considered to be the stone at all, the one in engagement rings was edged as the color Blue associated with loyalty has been.
One of the most popular engagement rings with sapphire is based in England. In 1981, Prince Charles Lady Diana put a ring with a 12-carat sapphire plus 14 ring-shaped ornaments on her finger. In October 2010, the jewel again gained public attention when Prince William presented the sapphire ring to Kate Middleton.


Sapphire healing stone

Just as long as sapphire is set in jewelry, the mineral is used as a healing stone.

Hildegard von Bingen already relied on the healing power of sapphire in her time. When choosing the healing stones that were important in the context of her healing stone studies, Hildegard von Bingen referred to stones that were both mentioned in the Bible and brought to her as well as through visions.

In Exodus 28: 17 to 21 of the Bible, sapphire is listed next to ruby, topaz, emerald, turquoise, jasper, hyacinth, agate, amethyst, chrysolite, carnelian and onyx, which adorn the apron of High Priest Aaron and symbolize the twelve tribes of Israel . Hildegard von Bingen expanded the stones so that they were also given the supposed healing power of sardonyx, prasem, chalcedony, chrysoprase, carbuncle, diamond, magnetite, Ligurius, crystal, river pearls, pearls, alabaster, lime, brick, gold, copper, silver Steel, lead, and brass worked.

Nowadays, sapphire is still offered as a chakra stone / healing stone, without the healing properties of sapphire being able to be confirmed in scientific studies.


Synthetic sapphire and fake sapphire

Not every sapphire that is offered in the gem market is a real sapphire. A first clue is the price, which is much higher for real sapphires than for imitations, syntheses or other colored minerals. A certificate provides information about the authenticity of a sapphire.

Very often sapphires are imitated by attaching blue foil to the underside of spinel, colored glass, garnet or rose quartz so that the impression of a blue sapphire is created. Set in jewelry and covered by claws, it is difficult to expose the deception at first glance.

The first sapphire synthesis was achieved in 1902 by melting a powder consisting of corundum, iron and titanium together. The sapphire formed in the so-called Verneuil process is very similar to real sapphires in terms of appearance and hardness.

Evidence of sapphire

Sapphires have a pronounced pleochroism. Blue sapphires appear green-blue to deep blue, while yellow sapphires turn yellow to yellow-green, and purple sapphires appear red-violet to light red. The fluorescence is given with the exception of blue sapphires. Yellow sapphires fluoresce in orange, colorless sapphires in orange and purple.
Sapphires are not soluble in acids. The corundum variety begins to melt at temperatures of 2,050 ° C.


miscellaneous

Sapphire, diamond and rock crystal are the monthly stones / birthstones for the month of April.
A cut sapphire also adorned a stamp issued by Deutsche Post in 2012. In addition to a sapphire (see Fig. 1), an emerald and ruby ​​were also featured on the welfare stamps under the title "Precious Stones".


Also interesting:
⇒ The value of sapphire
⇒ Blue diamonds
⇒ Lapis Lazuli


Swell:
⇒ Bauer, J .; Tvrz, F. (1993): The Cosmos Mineral Guide. Minerals rocks precious stones. An identification book with 576 color photos. Gondrom Verlag GmbH Bindlach
⇒ 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
⇒ Pellant, C. (1994): Stones and Minerals. Ravensburger nature guide. Ravensburger Buchverlag Otto Maier GmbH
⇒ Schumann, W. (1991): Minerals rocks - characteristics, occurrence and use. FSVO nature guide. BLV Verlagsgesellschaft mbH 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. (2017): Precious stones and gemstones. All kinds and varieties. 1900 unique pieces. BLV determination book, BLV Verlagsgesellschaft mbH Munich
⇒ Hochleitner, R. (2017): Which stone is that? Kosmos nature guide. Over 350 minerals, gemstones and rocks. Franckh Kosmos Publishing House
- News entry www.steine-und-minerale.de (January 2, 2012): Welfare brands precious stones
- www.mindat.org - sapphire
- www.dailymail.co.uk

Reading tip: www.lapisphilatelie.de - a collection of stamps with a focus on minerals and geology

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