Spinell
| Spinell | |
|---|---|
 | |
| Fakta | |
| Kategori | Mineral |
| Kemi | Magnesiumaluminat MgAl2O4 |
| Färg | Röd, Rosa, Mörkgrön, Gul, Violett, Orange, Blå, Svart |
| Streckfärg | Vit |
| Kristallsystem | Kubisk, spinellstruktur |
| Brott | mussligt, oregelbundet |
| Mohs | 8 |
| Ljusbrytning | 1,712-1,736 |
| Dubbelbrytning | 0,026 |
| Spaltning | Ofullständig |
| Densitet | 3,58-3,61 |
| Dispersion | 0,026 |
Spinell är ett mycket hårt mineral som består av magnesiumaluminat, MgO2(AlO)2, ibland med inblandning av krom och järn. Det har gett namn till mineralgruppen spineller med liknande typ av uppbyggnad och kristallstruktur.[1]
Egenskaper
Den ädla spinellen har röd färg i talrika nyanser. Dessutom förekommer gula, blå och gröna spineller i flera nyanser, samtidigt som det även förekommer en svart variant, som kallas pleonast eller ceylonit.
Spinell är mycket hård (8,0 på Mohs hårdhetsskala). Den bildar kubiska kristaller med så kallad spinellstruktur.
Förekomst
Trots att spinellen ursprungligen bildats i urbergets bergarter, oftast i kristallin kalksten, påträffas de klara, ädla varianterna främst i sandlager, på samma sätt som många andra ädelstenar.
De främsta fyndorterna finns i Myanmar, Sri Lanka och Thailand. Dock förekommer spineller även på många andra ställen tillsammans med safir, rubin, zirkon och andra ädelstenar.
Användning
Spinell används som ädelsten. Värdefullast är den röda spinellen, särskilt de nyanser, som till färgen står närmast rubin s.k. rubinspineller.
Fullkomligt ren och färglös spinell förväxlas ibland med diamant, då den har ungefär samma densitet och liksom denna är enkelbrytande.
Bilder
(c) Rob Lavinsky, iRocks.com – CC-BY-SA-3.0
(c) Rob Lavinsky, iRocks.com – CC-BY-SA-3.0Kristall i oktaederform
(c) Rob Lavinsky, iRocks.com – CC-BY-SA-3.0
(c) Rob Lavinsky, iRocks.com – CC-BY-SA-3.0Den stora gulbruna och den lilla röda är båda spineller i olika färgvarianter
Källor
- ^ H-J Meyer: Festkörperchemie i: H-J Meyer (red.), Riedel Moderne Anorganische Chemie, Walter de Gruyter, 2012, ISBN 978-3-11-024900-2. Läst 12 april 2018.
- Meyers varulexikon, Forum, 1952
Externa länkar
Wikimedia Commons har media som rör Spinell.
Wikimedia Commons har media som rör Media som används på denna webbplats
Författare/Upphovsman: Ingen maskinläsbar skapare angavs. S kitahashi antaget (baserat på upphovsrättsanspråk)., Licens: CC BY-SA 3.0
Spinel. 4.13ct and 1.83ct. taken by Azuncha.
(c) Rob Lavinsky, iRocks.com – CC-BY-SA-3.0
Norbergite, Spinel
- Locality: Mogok, Pyin Oo Lwin District, Mandalay Division, Burma (Myanmar) (Locality at mindat.org)
- Size: miniature, 4.9 x 2.9 x 1.7 cm
- Norbergite with Spinel
- This specimen features a GEMMY, translucent 1.3-cm norbergite crystal perched on matrix from which it has been excavated carefully. It is squarish in shape, fairly equant all around, and complete except for a slight conchoidal ding in the lower-right corner (shown at its worst in the second photo, to be clear, so you can se eit doesn't affect display view much at all). Little sharp red spinels grace it for accent. This is a SUPER crystal for the species, from any locality, and from Mogok its actually quite rare to find them. When I obtained these two specimens from an importer at Tucson, I showed them to a friend who came by soon after and deals in rare gems, as they were translucent. Indeed, he said they would cut unusually fine stones for the species, so here you have an "ugly" magnesium silicate with Cutting rough value ! Couldn't let him do it, so I held them back for sale to collectors, but the yield in gem value should work out to about this price anyhow.
Författare/Upphovsman: Sodabottle, Licens: CC BY-SA 3.0
Photo of an exhibit at en:Museum of Islamic Art, Doha Engraved spinel , India. c. 1628-1657, Spinel
(c) Rob Lavinsky, iRocks.com – CC-BY-SA-3.0
Spinel
- Locality: Gon Deposit, near Timpton River, Lena River Valley, Aldan, Aldan Shield, (Eastern Siberian, Russia
- Size: thumbnail, 2.6 x 2.4 x 2.3 cm
- Spinel
- This equant, sharp spinel crystal is free of damage, measuring 2.25 cm in each dimension, and beautifully terminated. It is totally complete except for a few minor contacts of attached matrix on back, and floats freestanding on a pedestal of natural matrix! It has a rich "satiny" lustre, characteristic of pocket-growth crystals that have never been covered by other rock, or calcite infill which has to be removed with acid. This locality historically produced spinels of this calibre, but I had never seen one of such size and in any case they came out 20 years and more ago. This new find at the same old locale has provided us a small new supply of these spinel classics. What is nice , though, is that the overall quality for this combination of size and crystal habit of spinel has not been surpassed in the meantime - they stand as important spinels, not just as interesting locality classics, in other words.
(c) Rob Lavinsky, iRocks.com – CC-BY-SA-3.0
Spinel
- Locality: near Helena, Montana
- Size: thumbnail, 2.6 x 1.8 x 1.8 cm
- Blue Spinel
- CLASSIC AND RARE, this is a great example of the blue spinel from Montana! Perched on white contrasting matrix, this rich royal blue, translucent, octahedron of spinel measures over 1.25 cm across. It displays a waxy or resinous luster.
(c) Rob Lavinsky, iRocks.com – CC-BY-SA-3.0
Pyrrhotite, Spinel
- Locality: Kuch-i-Lal, Ishkashim District, Western Pamir Mountains, Tajikistan
- Size: thumbnail, 3.0 x 2.7 x 2.3 cm
- Spinel on Pyrrhotite
- This is probably my favorite of the lot, for the sheer statrling contrast of the totally GEM CLEAR crystal on bright golden pyrrhotite (here, the contrast is most stark because the pyrrhotite is so bright and golden in color compared to others in the lot). This one features a dramatic single 7 mm gem crystal atop a perch of massive pyrrhotite. I had never seen spinel from here, nor spinel on pyrrhotite (or other sulfides) from anywhere. The contrast is striking and , luckily, the spinels are of gem quality so these are good specimens on their own and not just new "locality pieces." These gem crystals have a unique lavender hue that sets them apart from other spinels we have seen out of Mogok and Sri Lanka.