Introduction of opal
Opal is a naturally formed silica gel that contains between 5% and 10% moisture. Unlike most gemstones, opal is amorphous, meaning it lacks a crystalline structure. This makes it vulnerable to drying out over time, which can lead to cracking if the moisture content drops too low. In mineralogy, opal is classified as a hydrated amorphous silica, with the chemical formula SiO₂·nH₂O. According to the GIG Research Report, opal is known in English as "opal" and is also referred to as "Opal" or "Opal." It is a form of silica that contains water molecules within its structure. Because it is amorphous, opal does not have a defined crystal shape. Its fracture pattern is typically conchoidal, and it forms through the deposition of colloidal silica particles. When this process occurs within organic remains, such as shells or tree trunks, it can create unique varieties like "tree jade" or "spiral jade." These rare forms are sometimes found in Hainan, where they are called "snail fossil" or "sea jade," and are highly valued due to their scarcity. The refractive index of opal ranges from 1.37 to 1.47. This value is influenced by the water content—higher moisture levels result in a lower refractive index. Hardness: 5.5–6.5 on the Mohs scale Density: 2.15–2.23 g/cm³ Opal is typically white or colorless, but when other elements such as iron, calcium, magnesium, or copper are present, it can display a wide range of colors. Opal usually has a glassy or waxy luster. If the luster changes depending on the viewing angle, it becomes more valuable. Otherwise, it is considered a decorative stone rather than a high-quality gem. Opal often appears in dense, granular, earthy, stalactitic, tubercular, or porous forms. Its internal structure is spheroidal, and the aggregates may resemble grapes or stalactites. The background color can be black, milky white, light yellow, or orange, and it ranges from translucent to slightly transparent. It exhibits a glassy, pearly, or even protein-like luster and may display a color-changing effect, known as "play-of-color." Opal is relatively brittle and prone to drying out, with a conchoidal fracture. Different types of opal can emit various fluorescence under long-wave ultraviolet light. There are two main types of opal: precious opal and common opal. Precious opal is distinguished by its ability to display a play-of-color, also known as "color flash" or "iridescence." This effect is caused by the arrangement of tiny silica spheres within the gemstone, which diffract light and create a spectrum of colors. Larger silica spheres produce a broader range of colors, making the opal more valuable. The quality of an opal is evaluated based on its base color, color change, durability, and the quality of its cut and polish. Cement Additive,superplasticizer for cement,cement plasticizer retarder,acrylic polymer cement additive,waterproof cement additive Shanghai Hongyun New Construction Materials Co., Ltd , https://www.hongyunpce.com