I have observed many netizens’ comments on the evaluation of completely clear white crystal: ‘Isn’t this just glass?’ Indeed, visually, completely clear white crystal bears a strong resemblance to glass. So, what is the difference between crystal and glass? Additionally, there are numerous online tutorials on how to distinguish between crystal and glass, such as using a strand of hair to check for double images, leveraging the difference in hardness between glass and crystal to scratch each other, and so on. Are these methods reliable?
Essentially, crystal, a single-crystalline quartz gemstone, is a natural crystalline form of silicon dioxide, capturing different trace elements like iron, manganese, and titanium during its growth process, resulting in various colors. The formation of crystal requires stringent conditions; firstly, a conducive developmental environment is needed, such as underground cavities or fissures. In these cavities, temperature and pressure must be just right and stable, without fluctuating. Most importantly, there must be a certain amount of alkaline, low-salinity silicon dioxide ore-forming solution. Only then can crystals grow.
2. Minimum internal energy: This ensures that within the range of external energy that a crystal can withstand, its properties remain stable. For example, a crystal has a melting point. Only when it reaches 1713 degrees Celsius will the crystal start to melt, and its form will not change before that. However, when glass is heated, it will first soften as a whole and then turn into a fluid.
3.
4. Symmetry: A well-developed crystal has symmetry in terms of crystal face shape, size, and position, and its physical properties are the same. Isn’t the ideal crystal form of a crystal very symmetrical?
Appearance differences
External characteristics of raw crystal stones: A well-developed crystal has typical columnar crystals, with an external appearance of pseudo-hexagonal bipyramids.
Transverse striations on crystal faces: Raw natural crystal stones are often accompanied by transverse striations on the crystal faces, which are like the tree rings and are signs of step-by-step growth.
Etch figures: These are not the memories left by high priests, but rather the marks left by corrosion.
External characteristics of glass: The shape of natural glass is irregular, while the shape of artificial glass depends on the mindset of the processor. Natural glass, obsidian
Optical properties
Colors of crystal: The colors of crystals can be colorless, purple, yellow, pink, brown, green, etc.
Colors of glass: Colorless and any color, with a rich and diverse range of colors. The colors of crystals are very natural and comfortable to look at; the colors of glass are very gaudy and strange. From the color differences between crystals and glass, we can easily distinguish some glassy crystal imitations with strange colors, such as Japanese Andrew crystals and smelted crystals, etc.
Andrew Lightworker “crystals”, smelted crystals, glass balls with strange colors
Luster and transparency
Luster and transparency of crystals: Vitreous luster, and the fracture can have a greasy luster. Transparent to translucent.
Luster and transparency of glass: Vitreous luster. Transparent to opaque.
Special optical effects
Special optical effects of crystals: Cat’s-eye and star effects can be seen in crystals. Copper hair crystal, cat’s-eye
Special optical effects of glass: Some glass varieties can show cat’s-eye, aventurine, iridescence, and color-changing effects. Glass cat’s-eye stone, glass sandstone
Physical properties
Fracture
Fracture of crystals: Conchoidal fracture
Fracture of glass: Conchoidal fracture
The fractures of both crystals and glass are typically conchoidal fractures.
You can freely touch crystal fragments without any fear of cuts. The density of crystal is 2.66, while the density of glass ranges from 2.0 to 4.2. Unlike crystal, whose density is relatively constant, glass’s density can vary significantly. Adding lead or bismuth during processing can increase the relative density of glass. Thus, the statement that glass of the same size is lighter than natural crystal is clearly incorrect; glass’s density can be made higher or lower. Consequently, the weight can also vary. Relying on the sense of touch to judge the weight is unreliable because glass’s density can be made to exceed that of natural crystal. Moreover, your hands are not an electronic scale; how can you discern such minute differences? Mohs hardness of crystal is 7, while that of glass is around 5. Hardness is an indicator of a gemstone’s durability. Some say that airborne dust has a Mohs hardness of 7.5, which should be the passing grade for gemstone hardness. By this standard, crystal’s hardness cannot be considered excellent. However, when considering how few gemstones exceed a hardness of 7.5, only a handful come to mind, such as the big five gemstones. Crystal has a hardness of 7, whereas glass has a hardness of around 5. Therefore, the online method of comparing crystal and glass by inflicting damage on each other to see if marks are left is feasible. Nevertheless, I do not highly recommend this approach since its practicality is questionable. You cannot walk into a store to buy crystal while carrying a piece of glass to test it on the spot. Even if you purchase online, once you receive the item and scratch it with glass, and it shows marks, you know it’s fake, but the seller may still refuse your return request because you have damaged the product, affecting its resale. When examining crystal characteristics under magnification, you can observe color bands, fluid inclusions (two-phase and three-phase gas-liquid and gas-liquid-solid), negative crystals, as well as various solid inclusions such as rutile, tourmaline, garnet, fluorite, chlorite, epidote, hematite, and limonite. The impurities we often refer to as ‘cotton’ are also a type of inclusion. Most inclusions in crystal are natural, and artificial imitation is challenging, with even the best imitations not being very convincing. Glass characteristics: The advancement of modern manufacturing often results in cleaner glass interiors, which, upon close inspection, usually contain bubbles and swirl patterns. In summary, understanding crystal identification is a matter of accumulating experience and involves comprehensive knowledge, including gemological characteristics of crystals (examining color and inclusions), crystal morphology (observing external features), and the production and processing techniques of crystals. It even extends to price judgment. For example, a 5cm natural, pure white crystal sphere offered for only 100? This is clearly impossible, as the market price is in the thousands.
If you are faced with a string of all-pure white crystal bracelets or a Wuji card, which lacks natural crystal characteristics and glass features, how should you determine its authenticity? It is best to send it for professional testing.