Zoisite
| Zoisite | |
|---|---|
 (size: 7.5 × 4 × 2 cm) |
|
| General and classification | |
| chemical formula | Ca 2 Al 3 [O | OH | SiO 4 | Si 2 O 7 ] |
|
Mineral class (and possibly department) |
Silicates and germanates - group silicates (sorosilicates) |
|
System no. to Strunz and to Dana |
9.BG.10 ( 8th edition : VIII / B.15b) 58.02.01b.01 |
| Similar minerals | depending on the variety amethyst , cordierite , sapphire , spinel , eudialyte , carnelian , rhodonite , ruby |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Space group | Pnma (No. 62) |
| Lattice parameters | a = 16.19 Å ; b = 5.55 Å; c = 10.03 Å |
| Formula units | Z = 4 |
| Frequent crystal faces | (100), (101), (110) |
| Physical Properties | |
| Mohs hardness | 6 to 7 |
| Density (g / cm 3 ) | measured: 3.15 to 3.36; calculated: 3.35 |
| Cleavage | completely according to {100}, {001} |
| Break ; Tenacity | uneven or scalloped |
| colour | colorless, yellow, green, pink, red, blue, gray |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss, pearlescent gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.696 to 1.700 n β = 1.696 to 1.702 n γ = 1.702 to 1.718 |
| Birefringence | δ = 0.006 to 0.018 |
| Optical character | biaxial positive |
| Axis angle | 2V = 0 to 69 ° |
| Pleochroism | visible to strong (tanzanite): X = light pink to red-violet Y = almost colorless to strong pink or deep blue Z = light yellow to yellow-green |
| Other properties | |
| Special features | sensitive to heat, color changes possible |
Zoisite (also Saualpit ) is a rather seldom occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the orthorhombic crystal system with the chemical composition Ca 2 Al 3 [O | OH | SiO 4 | Si 2 O 7 ], that is a complex calcium - aluminum silicate with additional oxygen - and hydroxide ions . Structurally, zoisite belongs to the group silicates (sorosilicates).
Zoisite usually develops transparent to translucent crystals of up to 10 cm in length and a prismatic habit , which are often striped lengthways. Massive, granular or radial mineral aggregates are also known.
With a Mohs hardness of 6 to 7, zoisite is one of the medium-hard to hard minerals. At least a steel file is required to scratch it, but it is able to scratch simple window glass itself .
Pure zoisite is colorless, but it can be gray to yellow, green, pink to red or blue to purple in color due to various admixtures. The line color of the zoisite, however, is always white. Undamaged, smooth crystal surfaces have a lively, glass-like sheen , whereas cleavage surfaces have a more mother-of-pearl shimmer .
Is known primarily for his Zoisit Gem - varieties tanzanite (blue-violet) and Thulit (pink).
Etymology and history
The mineral was first discovered by a mineral dealer (presumably Simon Preschern) at the so-called "Prickler Halt", a ridge between Speikkogel and Ladinger Spitz in the Austrian state of Carinthia, who initially referred to the find as Saualpit based on its type of locality and it to the entrepreneur and natural scientist Sigmund Zois Baron von Edelstein (1747-1819) handed over, who had supported the mineral dealer's research trip.
However, Zois suspected that this was a new, previously unknown type of mineral and informed the mineralogist Abraham Gottlob Werner (1749–1817) and Martin Heinrich Klaproth (1743–1817) about this find, who were able to confirm his assumption. In 1805 Werner gave the new mineral the name Zoisite, which is still recognized today, in honor of Zois.
classification
Already in the outdated 8th edition of the mineral classification according to Strunz , the zoisite belonged to the mineral class of "silicates and germanates" and there to the department of "group silicates (sorosilicates)", where it was the only member of the zoisite subgroup with system no. VIII / B.15b within the "epidote-zoisite group".
In the last revised and updated Lapis mineral directory by Stefan Weiß in 2018 , which, out of consideration for private collectors and institutional collections, is still based on this classic system of Karl Hugo Strunz , the mineral was given the system and mineral number. VIII / C.23-100 . In the "Lapis system" this also corresponds to the division of "group silicates", where zoisite together with allanite (Ce) , allanite (La) , allanite (Nd) , allanite (Y) , Alnaperbøeit (Ce) , Ascagenite (Nd) , dissakisite (Ce) , dissakisite (La) , dollaseite (Ce) , epidote , epidote (Sr) , ferriadrosite (La) , ferriakasakaite (La) , ferricallanite (Ce) , Ferriallanite- (La) , Ferriperbøeit- (Ce) , Gatelite- (Ce) , Hancockite , Khristovite- (Ce) , Klinozoisite , Manganiakasakaite- (La) , Manganiandrosite- (Ce) , Manganiandrosite- (La) , Mukhinite , Niigataite , Perbøeit- (Ce) , Piemontit , Piemontit- (Pb) , Piemontit- (Sr) , Tweddillit , Uedait- (Ce) , Vanadoallanit- (La) , Vanadoandrosit- (Ce) and Västmanlandit- (Ce) , the "epidote Group "forms.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also classifies the zoisite in the group of "group silicates". However, this is further subdivided according to the type of group formation of the silicate complexes and the coordination of the cations , so that the mineral is classified according to its composition and structure in the subdivision of “group silicates with mixed SiO 4 and Si 2 O 7 groups; Cations in octahedral [6] and greater coordination ”can be found, where it is the only member of the unnamed group 9.BG.10 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , also assigns the zoisite to the class of "silicates and Germanates", but there in the more finely divided division of "group silicates: insular, mixed, individual and larger tetrahedral groups". Here he is the only member of the "epidote group (zoisite subgroup)" with the system no. 58.02.01b within the subdivision of “ Group Silicates : Insular, mixed, single and larger tetrahedral groups with cations in [6] and higher coordination; Single and double groups (n = 1,2) ”.
Crystal structure
Zoisite crystallizes dimorphically with clinozoisite in the orthorhombic crystal system in the space group Pnma (space group no. 62) with the lattice parameters a = 16.19 Å ; b = 5.55 Å and c = 10.03 Å and 4 formula units per unit cell .
properties
Similar to cordierite, zoisite has a clearly visible pleochroism , which can be very strong, especially in the tanzanite variety :
Zoisite is sensitive to heat and reacts to it with a change in color, which is exploited, among other things, by converting the gray-brown zoisite, which is mostly found in the mines, into the coveted blue tanzanite by firing at around 550 ° C.
Modifications and varieties
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Several varieties of zoisite are known:
- Tanzanite - blue to blue-violet, firstfoundin Tanzania in 1967
- Thulite - red due to the addition of manganese . However, some of the thulites described are varieties of clinozoisite .
Anyolite (h) (also zoisite rock ), on the other hand, is an aggregate or, better, rock of green zoisite, red, opaque ruby and often also with inclusions of black hornblende (minerals of the amphibole group ).
Education and Locations
Zoisite is formed through metamorphosis in calcium- rich rocks such as pyroxene , gneiss or amphibolite , but also through contact metamorphosis in marble . Accompanying minerals include various garnets and horn blends , albite , biotite , calcite and quartz .
As a rather rare mineral formation, zoisite can sometimes be abundant at various sites, but overall it is not very common. Around 1000 sites are known to date (as of 2015). In addition to its type locality "Prickler Halt" in the Saualpe , the mineral was also found in Austria in Hüttenberg , the Gurktal Alps , near Moosburg , on Lake Millstatt and near Winklern in Carinthia; near Badersdorf in Burgenland; near Dunkelsteinerwald and in the Waldviertel in Lower Austria; in the Hohe Tauern from Carinthia to Salzburg, the Kitzbühel Alps ; on the Koralpe from Carinthia to Styria; found on the Packalpe and near Stubenberg in Styria as well as in the Virgen , Inn , Ötz and Zillertal in Tyrol.
In Germany, zoisite was found near Bötzingen in Baden-Württemberg; in several places in Franconia , Lower Bavaria and the Upper Palatinate in Bavaria; in the Hessian Odenwald ; in the Harz region of Lower Saxony ; found in the Eifel in Rhineland-Palatinate and in the Saxon Ore Mountains .
In Switzerland, the mineral has so far been found in the Valle Maggia and Valle Verzasca in Ticino and in the Valais in the Binn valley , near Brig , Martigny and Zermatt .
Other locations include the Antarctic , Australia , Belgium , Brazil , Chile , China , Finland , France , Greece , Greenland , Guatemala , India , Ireland , Italy , Jamaica , Japan , Canada , Kazakhstan , North and South Korea , Madagascar , Mexico , New Zealand , Norway , Oman , Pakistan , Paraguay , Poland , Romania , Russia , Sweden , Zimbabwe , Slovakia , Slovenia , Spain , South Africa , Taiwan , Tanzania , Czech Republic , Turkey , Ukraine , Hungary , the United Kingdom (Great Britain) and the United United States of America (USA).
Use as a gem stone
The rare varieties tanzanite and thulite are known and sought-after as gemstones , but varieties of other colors can also be cut into beautiful gemstones if they are of good quality, i.e. clear and low-inclusion quality .
However, since the mineral is sensitive to excessive and uneven heating, barrel and repair work must be carried out carefully. Even the touch of the stone with the soldering flame can z. B. lead to blistering and cause it to swell.
See also
literature
- Petr Korbel, Milan Novák: Mineral Encyclopedia (= Villager Nature ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 216 .
- Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th, revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 176 .
Web links
- Zoisite , thulite and tanzanite in the mineral atlas (Wiki)
- Michael RW Peters: Zoisite. In: realgems.org. April 5, 2012, accessed December 5, 2019 (with examples of cut zoisites).
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 587 (English).
- ↑ David Barthelmy: Zoisite MineralData. In: webmineral.com. Retrieved December 5, 2019 .
- ↑ a b c Zoisite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 79 kB ; accessed on December 5, 2019]).
- ↑ a b c d e Zoisite. In: mindat.org. Hudson Institute of Mineralogy, accessed December 5, 2019 .
- ↑ Ernest Faninger: The discovery of the zoisite . In: Geologija . tape 28/29 , 1985, pp. 337–342 , urn : nbn: si: DOC-JRAMEFGW ( prenit.geo-zs.si [PDF; 21 kB ; accessed on April 24, 2020]).
- ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
- ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1816 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed December 5, 2019 .
- ↑ Bernhard brother embellished stones. Recognizing imitations and manipulations in gemstones and minerals . Neue Erde, Saarbrücken 2005, ISBN 3-89060-079-4 , p. 101 .
- ↑ Localities for Zoisite. In: mindat.org. Hudson Institute of Mineralogy, accessed December 5, 2019 .
- ↑ List of locations for zoisite in the Mineralienatlas and Mindat , accessed on December 5, 2019.
- ^ Precious stone etiquette from Prof. Leopold Rössler - Tanzanite. In: beyars.com. Retrieved December 5, 2019 .