Celadonite
| Celadonite | |
|---|---|
 |
|
| General and classification | |
| other names |
Celadonite |
| chemical formula | K (Mg, Fe 2+ ) (Fe 3+ , Al) [(OH) 2 | Si 4 O 10 ] |
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.EC.15 ( 8th edition : VIII / H.10) 71.02.02a.06 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m or monoclinic sphenoid; 2 |
| Space group | C 2 / m (No. 12) or C 2 (No. 5) |
| Lattice parameters |
a = 5.22 Å ; b = 9.05 Å; c = 10.20 Å β = 100.4 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 2 |
| Density (g / cm 3 ) | 3.00 to 3.05 |
| Cleavage | completely after {001} |
| Break ; Tenacity | crumbly |
| colour | light green to blue-green |
| Line color | White |
| transparency | translucent to opaque |
| shine | frosted |
| Crystal optics | |
| Refractive indices |
n α = 1.606 to 1.625 n β = 1.630 to 1.662 n γ = 1.579 to 1.661 |
| Birefringence | δ = 0.027 |
| Optical character | biaxial negative |
| Axis angle | 2V = 5 to 8 ° |
| Pleochroism | visible: x = yellowish green; y and z = green to emerald green |
Celadonite (engl: Celadonite ), synonymous or as pigment also known as green earth (mainly celadonite and glauconite existing batch) Veronesererde , Veronesergrün , Tyrol earth known, is a common mineral of the mineral class of " silicates and germanates ". It crystallizes in the monoclinic crystal system with the chemical composition K (Mg, Fe 2+ ) (Fe 3+ , Al) [(OH) 2 | Si 4 O 10 ] and develops predominantly earthy to massive mineral aggregates , but rarely also tiny, mica-like, flaky crystals of light green to blue-green color and white streak color . The celadonite is often found intimately interwoven with heulandite or stilbite and provides these normally colorless minerals with an even, sea-green color.
Celadonite has served as a green pigment since ancient times .
Etymology and history
Celadonite was first described in 1847 by Ernst Friedrich Glocker , who named the mineral after the French word “céladon” for sea green because of its characteristic color .
A total of three type localities are given for celadonite : Planitz in Saxony (Germany), "Malga Canalece" near Brentonico and "Tierno-Besagno" near Mori on Monte Baldo in the Italian province of Trentino . The reason for this is that several samples from the named sites had to be used to determine the mineral.
classification
In since 2001 outdated, but still in use 8th edition of the nomenclature of minerals by Strunz of seladonite is part of the department of " phyllosilicates (phyllosilicates)" and then to " mica group , subgroup Seladonit- muscovite series".
Since the revision of Strunz's mineral system in the 9th edition , the phyllosilicates have been subdivided more precisely according to the structure of the silicate layers and the mineral can be found accordingly in the subdivision of "phyllosilicates with mica panels, composed of tetrahedral and octahedral networks", where it is a member of the glauconite group with system no. 9.EC.15 is.
The systematics of minerals according to Dana also sorts the celadonite into the division of layered silicates and also in the systematics of Dana is further specified according to the crystal structure. However, the subdivision is described here as "layered silicates with layers of six-membered rings with 2: 1 layers". The mineral is found there in the " mica group (muscovite subgroup) " with the system no. 71.02.02a .
Crystal structure
Celadonite crystallizes monoclinically in the space group C 2 / m (space group no. 12) or C 2 (no. 5) with the lattice parameters a = 5.22 Å ; b = 9.05 Å; c = 10.20 Å and β = 100.4 ° and 2 formula units per unit cell .
Education and Locations
Celadonite is mainly formed in alkaline volcanic rocks by hydrothermal processes , where it primarily replaces iron and magnesium-containing silicates. Accompanying minerals include calcite , various chlorites , various heulandites , clinoptilolite , laumontite , montmorillonite , prehnite and quartz .
Celadonite occurs in different locations and shows different nuances depending on where it was found, such as chip, bluish and celadon green, olive, apple or gray green. The best-colored celadonites come from Monte Baldo near Verona , where they can be found in large quantities.
Other sites are in Trentino (Fassatal) and Tyrol (Zillertal), in the Harz Mountains , in Thuringia , Bohemia , Poland and Hungary , in Scotland (Scuir Mohr) and on the Faroe Islands (Streymoy, Suduroy). Occurrences in North America include a. in Oregon (John Day Formation), at Mt. Rainier National Park (Wash.), California (Red Rock Canyon) and Nicaragua as well as in Japan (prefectures Miyagi, Yamagata, Kamogawa and Chiba). So far (as of 2010), celadonite has been found at around 200 sites worldwide.
A well-known site is also the Monte Altissimo di Nago , the 2079 m high northern summit of Monte Baldo with a celadonite outcrop in which the pigment “ green earth ”, which was already used in ancient times as “terra verdi”, is found.
use
Celadonite or green earth has been used as a pigment since ancient times and is still finely slurried to make very durable, colorfast and harmless colorants for paints and paintings, both as oil paint and glue paint . Moderate glow turns their color into a beautiful brown.
See also
literature
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 750 (first edition: 1891).
- Petr Korbel, Milan Novák: Mineral Encyclopedia (= Villager Nature ). Nebel Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 250 .
- Celadonite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 74 kB ]).
Web links
- Mineral Atlas: Celadonite (Wiki)
- Kremer-Pigmente GmbH - celadonite , green earth and Veronese green earth
Individual evidence
- ↑ a b c d e f 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. 665 .
- ↑ a b Webmineral - Celadonite (English)
- ↑ a b c d e f Mindat - Celadonite (English)
- ^ Mineralienatlas: type locality
- ↑ Mindat - Localities for Celadonite
- ↑ Entry on green earth. In: Römpp Online . Georg Thieme Verlag, accessed on May 23, 2013.
- ↑ Uni Bayreuth - Colors and Light ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; on the color fastness of celadonite: p. 17; 6.2 MB)
