In ceramics it acts as a flux which imparts the vitreous lustre to chinaware, sanitaryware and ceramic tiles. It is used in glazes and enamels, and is an important mineral filler in paints, plastics, sealants and adhesives.
Pegmatites are found in all outcropping areas of Precambrian and early Palaeozoic rocks throughout the State, but the only significant production has been from deposits in the Mount Lofty Ranges and Olary Province. South Australia produced about tonnes of ablbite, an ornamental aggregate, from the Antro Deposit in the Olary Province in From to , 14 t of feldspar were mined from a partly kaolinised quartz—feldspar—muscovite pegmatite near the western margin of the Mount Crawford kaolinite—sillimanite orebody during a phase of quarry expansion.
Three types of feldspar deposits are hosted by Willyama Supergroup rocks in the Olary region Fig. In glassmaking , Imerys feldspars are excellent fluxing agents for flat and container glass, as well as for insulation wools. Feldspar is an excellent source of alumina which improves end product hardness, durability, and resistance to chemical corrosion. Used in ceramics , feldspar and pegmatite are the main vitrifying or fluxing agent used during the firing process of ceramic bodies.
Fluxes melt at an early stage in the firing process forming a glassy matrix that bonds the other components of the system together, ensuring the durability of fired bodies. Imerys feldspars contain low levels of colored oxides, so they are particularly prized for white tiles and sanitaryware production.
The phenomenal properties of moonstone, sunstone and labradorite are almost always cut as dome-shaped cabochons. Their phenomenal properties are dependent upon light striking microscopic structures within a polished stone at just the right angle. To make that happen, skilled craftsmen who understand the optical phenomena of these gems must study the rough and cut the stone so that the planes where the optical phenomena are produced are parallel to the bottom of the cut gemstone.
Alert cutters might notice rare chatoyancy or asterism in moonstone rough. With proper planning, orientation, and skillful cutting, this rough can be used to produce cabochons that exhibit a cat's eye or a four-ray star. Moonstone is the best known of the phenomenal feldspars, but it is not found in many popular jewelry stores. All three of these gems are best found at gem and lapidary shows or at stores that specialize in unique and interesting gems and jewelry.
They can be easily found online; however, it is best to buy these stones or jewelry set with them where you can pick them up, play them in the light, and examine the strength, color and pattern of the optical effect.
If you have a number of pieces to select from, examine many of them because one or several of them will appeal to you much more strongly than the others - and different stones will appeal to different people.
It is best not to leave this to a random selection by the vendor or a friend. You will be happiest if you pick the one that appeals to your eye. Amazonite cabochons: Amazonite is a trade name for a green to bluish-green variety of microcline feldspar that is often cut into cabochons, beads and tumbled stones.
Faceted feldspar: Two specimens of labradorite feldspar that have been cut into faceted stones. Specimens from Oregon are often called "sunstone" - even nonphenomenal specimens without the aventurescence that many people believe is needed to merit the "sunstone" name. Although phenomenal feldspars are hard to compete with, there are a few other feldspars that make noteworthy gemstones. These are also best found at gem and lapidary shows or stores that specialize in interesting and different types of gems and jewelry.
Amazonite is a trade name for a green to bluish-green variety of microcline feldspar that is often cut into cabochons , beads and tumbled stones. The green color is caused by trace amounts of lead within the mineral. A world-famous locality for amazonite crystals is in the Freemont, El Paso and Teller Counties area of Colorado where it is found growing with smoky quartz in cavities of igneous and metamorphic rocks.
Although the name "amazonite" suggests that Brazil is a major source of the material, it is not found in the Amazon Basin. Feldspar minerals are often found in transparent crystals of gem quality. Orthoclase, labradorite and oligoclase are examples of feldspar minerals that have been faceted. Gemstones cut from these minerals can be beautiful; however, they are rarely seen in jewelry because they are not well known and requested by jewelry customers.
In addition, faceted feldspars have durability concerns because of their Mohs hardness of 6 to 6. Most feldspars that are faceted are for the "collector gems" market. Home » Minerals » Feldspar Feldspar A large group of silicate minerals.
The most abundant group of minerals in Earth's crust. Article by: Hobart M. Also colorless, yellow, orange, red, black, blue, green. Streak White Luster Vitreous. Pearly on some cleavage faces. Diaphaneity Usually translucent to opaque. Rarely transparent. Cleavage Perfect in two directions. Cleavage planes usually intersect at or close to a 90 degree angle. Mohs Hardness 6 to 6. Consistent hardness, specific gravity and pearly luster on cleavage faces.
Chemical Composition A generalized chemical composition of X Al,Si 4 O 8 , where X is usually potassium, sodium, or calcium, but rarely can be barium, rubidium, or strontium. Crystal System Triclinic, monoclinic Uses Crushed and powdered feldspar are important raw materials for the manufacture of plate glass, container glass, ceramic products, paints, plastics and many other products. Varieties of orthoclase, labradorite, oligoclase, microcline and other feldspar minerals have been cut and used as faceted and cabochon gems.
Star Moonstone: A moonstone cabochon that exhibits a rare four-ray star. Feldspar Information [1] What is Feldspar? It is the single most abundant mineral group on Earth. The minerals included in this group are the orthoclase, microcline and plagioclase feldspars. Feldspar processors reported co-product recovery of mica and silica sand. Feldspar is mined from large granite bodies called plutons by geologists , from pegmatites formed when the last fluid stages of a crystallizing granite becomes concentrated in small liquid and vapor-rich pockets that allow the growth of extremely large crystals , and from sands composed mostly of feldspar.
Present mines worldwide are adequately meeting the need for raw feldspar.
0コメント