I. Introduction to Natural Tourmaline

II. Gemstone Characteristics

1. Diverse Colors
   • Tourmaline encompasses almost the entire spectrum of colors, including red, green, blue, yellow, orange, purple, black, colorless, and many others. Among them, red tourmaline, also known as "Rubellite", has a bright and eye-catching color and is a relatively precious variety of tourmaline. Green tourmaline varies in color from light green to dark green, and some have a bluish tint, like chrome tourmaline, which has a rich color and a unique luster.
   • Bi-colored or multi-colored tourmaline is also common. For example, watermelon tourmaline has a pink center and a green edge, just like the flesh and rind of a watermelon. This unique color distribution is caused by the difference in the distribution of trace elements during the growth of tourmaline.
2. Transparency
   • The transparency of tourmaline varies widely, ranging from almost opaque to completely transparent. High-quality tourmaline usually has good transparency, allowing light to pass through the interior of the gemstone well, making the gemstone look brighter and more vivid. Semi-transparent tourmaline may have a soft luster, giving a warm feeling.
3. Hardness
   • Tourmaline has a Mohs hardness between 7 and 7.5, which gives it a certain degree of wear resistance. Compared with gemstones with lower hardness, tourmaline is less likely to be scratched during daily wear and can maintain a good surface finish. However, its hardness is still lower than that of diamond (Mohs hardness 10) and corundum (Mohs hardness 9), so it is still necessary to avoid intense friction with gemstones or objects of higher hardness when wearing and storing it.
4. Luster
   • Tourmaline has a vitreous luster. This luster enables it to reflect bright light under the illumination of light, enhancing the visual appeal of the gemstone. When light shines on tourmaline from different angles, its vitreous luster can create a twinkling effect on the surface of the gemstone, like little dots of light, making tourmaline even more dazzling.
5. Refractive Index
   • Tourmaline has a refractive index ranging from 1.624 to 1.644, which means it can effectively refract light. When light enters the interior of tourmaline, due to the effect of its refractive index, the direction of light propagation will change, thus creating a sense of internal brightness and depth. This optical property enables tourmaline to exhibit unique optical effects in jewelry, for example, in some well-cut tourmaline jewelry, you can see the internal light twinkling as if there is a small light source inside the gemstone.
6. Pleochroism
   • Tourmaline has obvious pleochroism, which means that different colors can be seen when observing tourmaline from different directions. For example, some blue tourmaline may appear dark blue from one direction and light blue or blue with a greenish tint from another direction. This pleochroism adds more interest and uniqueness to tourmaline and also provides an important basis for gemstone identification.
7. Pyroelectricity and Piezoelectricity
   • Tourmaline is a gemstone with pyroelectricity and piezoelectricity. Pyroelectricity refers to the generation of electric charge when tourmaline experiences a change in temperature, while piezoelectricity refers to the generation of electric charge when tourmaline is subjected to pressure. These characteristics make tourmaline valuable in some special application scenarios, such as in scientific research and certain electronic devices. However, in the application of jewelry, this characteristic is mainly known as an interesting scientific phenomenon.