The characteristic blue color arises mainly from caged S − 3 and S 4 clusters. The sodium can be replaced by other alkali group elements, and the chloride by other halides. ![]() Natural sodalite holds primarily chloride anions in the cages, but they can be substituted by other anions such as sulfate, sulfide, hydroxide, trisulfur with other minerals in the sodalite group representing end member compositions. This adds symmetry (such as mirror planes in the faces of the unit cell) so that the space group becomes Pm 3n ( space group 223), and the cavities cease to be chiral and take on pyritohedral symmetry. A discontinuity of the thermal expansion coefficient occurs at a certain temperature when chloride is replaced by sulfate or iodide, and this is thought to happen when the framework becomes fully expanded or when the cation (sodium in natural sodalite) reaches the coordinates (1/4, 1/4, 1/4) (et cetera). a reflexion, inversion, or improper rotation) can superimpose the silicon atoms onto silicon atoms and the aluminum atoms onto aluminum atoms, while also superimposing the sodium atoms on other sodium atoms. In this structure the two cavities are still chiral, because no indirect isometry centred on the cavity (i.e. As the temperature is raised the sodalite structure expands and uncrumples, becoming more like this structure. The structure is a crumpled form of a structure in which the three-fold axes of each tetrahedron lie in planes parallel to the faces of the unit cell, thus putting half the oxygen atoms in the faces. The six-membered rings can serve as channels in which ions can diffuse through the crystal. The three silicon atoms and the three aluminum atoms listed above closest to a given corner of the unit cell form a six-membered ring of tetrahedra, and the four in any face of the unit cell form a four-membered ring of tetrahedra. All the oxygen atoms are equivalent, but one half are in environments that are enantiomorphic to the environments of the other half. ![]() ) Each oxygen atom links between an SiOĤ tetrahedron. (A similar structure called "carbon sodalite" may occur as a very high pressure form of carbon - see illustration in reference. The silicon and aluminum atoms are located at the corners of a truncated octahedron with the chloride and four sodium atoms inside. There are four sodium ions around each chloride ion (at one distance, and four more at a greater distance), surrounded by twelve SiOĤ tetrahedra. Each cavity has chiral tetrahedral symmetry, and the cavities around these two chloride locations are mirror images one of the other (a glide plane or a four-fold improper rotation takes one into the other). One chloride is located at the corners of the unit cell, and the other at the centre. There is one cavity around each chloride ion. Each unit cell has two cavities, which have almost the same structure as the borate cage (BĢ, and as in the similar mineral tugtupite ( Naġ2Cl) (see Haüyne#Sodalite group). (There may be small amounts of other cations and anions instead.) This framework forms a zeolite cage structure. ![]() It is a cubic mineral of space group P 43n ( space group 218) which consists of an aluminosilicate cage network with Na + cations and chloride anions in the interframework. The structure of sodalite was first studied by Linus Pauling in 1930. Sodalite is a member of the sodalite group with hauyne, nosean, lazurite and tugtupite.įirst discovered by Europeans in 1811 in the Ilimaussaq intrusive complex in Greenland, sodalite did not become important as an ornamental stone until 1891 when vast deposits of fine material were discovered in Ontario, Canada. ![]() Although massive sodalite samples are opaque, crystals are usually transparent to translucent. d ə ˌ l aɪ t/ SOH-də-lyte) is a tectosilicate mineral with the formula NaĢ, with royal blue varieties widely used as an ornamental gemstone. Tenebrescent violet-red or green fading to white Soluble in hydrochloric acid and nitric acid Rich royal blue, green, yellow, violet, white veining commonĬommon on forming pseudohexagonal prismsīright red-orange cathodoluminescence and fluorescence under LW and SW UV, with yellowish phosphorescence may be photochromic in magentasĮasily to a colourless glass sodium yellow flame
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