Quartz
Alpha- quartz (low temperature quartz) and beta-quartz (high temperature quartz) are two homogeneous multi-image variants of SiO 2 . The beta quartz is stable in the range of 573 to 870 ° C, and below 537 ° C will be converted to α-quartz. Therefore, the quartz seen in nature is often α-quartz. "Quartz", which is usually not specifically described, means α-quartz. [Chemical composition] The chemical composition is relatively pure, but quartz often contains different amounts of mechanical mixture of gaseous, liquid and solid substances. [Crystal Structure] Trigonal System, Figure Y-16 Quartz crystal (quoted from Pan Zhaoyu et al., 1993) Figure Y-17 Crystal Cluster (a) (b) Figure Y-18 Quartz of quartz (quoted from Pan Zhaoyu et al., 1993) (a) Daofen twin crystal, (b) Brazilian twin crystal The most common twins are doxorubicin and Brazilian twins (Figure Y-18). These two twin crystals are very similar in appearance to a single crystal. The dodecene twin crystal has a c-axis as a twin-crystal axis, and is composed of two right-shaped crystals or two left-shaped crystals; the Brazilian twin crystal is a double crystal plane (1120), consisting of a left crystal and a The right-shaped crystal consists of a through-crystal, and these twins can be determined according to the distribution of the x-plane (trigonometric aspect). Since the x-plane on the single crystal appears once every 120° around the c-axis, if it occurs once every 60°, it must be a dodecene twin. In this case, if the two single crystals constituting the twin crystal are left-shaped crystals, they are double-rotating phenanthrene twin crystals (see Fig. Y-18(a)); when they are right-shaped crystals, they are right-handed fluorene twin crystals. . In the ideal case, if the two x-planes are symmetrically distributed in a left-right relationship, it means that it is formed by a left-shaped crystal and a right-shaped crystal. It should be a Brazilian twin (see Figure Y-18(b)). In addition, the double-crystal suture is generally curved on the doffer twin crystal, and is generally a fold line on the Brazilian twin crystal. If the quartz crystal is cut perpendicular to its c-axis, the cross-section is polished and corroded with hydrofluoric acid. After drying, observe the reflection on the section. If there is twin crystal, you can see the double pattern of the image. The eclipse pattern of the Dove is also curved in the shape of an island, while the Brazilian twin is a complex line pattern. In addition, it can also be distinguished directly by the crystal eclipse pattern: the etch pit orientation is different on the same cylinder on both sides of the suture, and if there is a quadratic axis between the etch pits on both sides, it is a dodecene twin crystal. If there is a symmetry plane between the two etch pits, it is a Brazilian twin. The two planes of Dove's twin crystals have the same direction of rotation, either left-handed or right-handed, so they can still be used as optical materials, but they are useless on piezoelectric materials, also known as electric twins; Brazilian twins It can neither be used as a piezoelectric material nor as an optical material, or optical twin. Figure Y-19 Japanese Twin Crystal (According to Pan Zhaoyu et al., 1993) Further, there are occasionally Japanese twin crystals in which (1122) is a double crystal plane and two monomers are obliquely intersected with each other along the c-axis by 84° 33' (Fig. Y-19). The aggregates are in the form of clusters, combs, granules, and dense blocks. The cryptocrystalline aggregates are called shells, kidneys, scorpions, and spheroids. They are called stone or chalcedon. They are called cherries, which have concentric bands and are made of multi-colored stone. The parallel arrangement of layers is called agate . [Physical properties] A variety of colors, often colorless, milky white, gray. Due to various impurities, the colors are different, and the following types are different: Rock crystal: colorless and transparent. Amethyst: Purple transparent or translucent, heated to decolorize. The reason for coloration may be caused by Fe 3+ generation Si. Rose quartz: light rose, dense and translucent. The reason for coloration may be caused by Al 3+ and Ti 4+ instead of Si. Smoky quartz: smoked or brown transparent. The reason for coloration is that under the action of radiation, Si is replaced by Al to cause the tetrahedron to produce a paramagnetic center defect. The color is further deepened to become black quartz Citrine: golden yellow or lemon yellow. The coloration may be caused by the inclusion of Fe 2+ . Milky quartz: milky white, translucent. Due to the fine dispersion gas, liquid inclusions and fine cracks. Those who are stained by solid inclusions have the following heterogeneity: Green onion stone: Containing green needle-shaped actinite inclusions, light green. Aventurine: with small inclusions of mica, iron ore and other red, pale yellow or brownish red. Opal, tiger eye, eagle eye: in various shades of dark, silky luster, like opal, tiger eye (yellow-brown) or eagle eye (blue-green), are due to quartz accommodating fiber asbestos To. Jasper: A dense block of red, yellowish brown, and green opaque. Blood chalcedony (also known as blood drop stone, blood stone, bloodstone): green stone marrow jasper, containing red spots. Glass luster; fracture grease luster. No cleavage, shell-like fracture. Hardness 7. The relative density is 2.65. It is piezoelectric. [Cause and occurrence] Alpha quartz is widely distributed in nature. It is the main rock-forming mineral of many igneous, sedimentary and metamorphic rocks. The quartz is the main mineral component of the granitic pegmatite vein and most hydrothermal veins. In quartz veins in the Weijing vein and metamorphic rocks, α-quartz is an important source of natural piezoelectric crystals. Some subtypes of quartz often have certain formation conditions or specific occurrences. Such as smoke crystal can only be formed at higher temperatures; amethyst is formed under relatively low temperature and pressure conditions; rose quartz is always produced in bulk at the core of the pegmatite vein; agate is a colloid of low temperature hydrothermal fluid The causative product is mainly produced in the pores of the erupted rock.  [Identification characteristics] α-quartz is characterized by its crystal form, no cleavage, shell-like fracture and hardness.  [Main use] It is widely used. The portion of the crystal without any inclusions, no twins or cracks (not less than 6 mm × 6 mm × 6 mm) is used as a piezoelectric material for making quartz resonators (such as quartz watches). In addition, crystal is an important optical material that also has good transparency to the infrared and ultraviolet portions of the spectrum for the production of spectral prisms, lenses and other optical material devices. Agate, amethyst, rose quartz and other precious jade material can be used. Agate and stone pulp with poor color are used to make abrasive tools. The purer general quartz is used in large quantities as glass raw materials, abrasive materials, silicon refractories and porcelain ingredients.
EVA Puzzle Mat is always a classic and
necessary educational toys for baby or children.
Made from Eco-friendly, closed cell,
non-smell and non-toxic EVA foam material, Melors promises that the foam puzzle mat
we offer is no harm to baby or children even many people is worry about the
safe of EVA foam product. We have passed ASTM and EN71 certificates for our EVA play mat, the certificates are available if customers need to have a look.
We have multiple educational puzzle mat designs like
numbers, letters, animals and vehicles for options, these are the basic and
common factors in the life, which is very good for the pre-school education for
baby and children, also as a safe and comfortable baby play mat applied in house.
If customer is interested in customized
design of the baby puzzle mat, please also feel free to let us know, we are capable to
produce the puzzle mat based on customized design, even the puzzle mat with a
full printing.
Eva Puzzle Mat,Baby Puzzle Mat,Eva Kids Puzzle Mat,Puzzle Floor Mat,Eva Jigsaw Mat,Educational Puzzle Mat Huizhou City Melors Plastic Products Co., Limited , https://www.foamexpert.net
a 0 =0.491 nm, c 0 =0.541 nm; Z=3. The [SiO 4 ] tetrahedron is linearly distributed in parallel with the c-axis. There is a left-right rotation, that is, the c-axis is 3 1 or 3 2 . The left and right rotations of the structure are opposite to the left and right shapes of the form (Fig. Y-16), that is, the right-shaped crystal is structurally left-handed, and the left-shaped crystal is structurally right-handed. 