Rock Discoveries

Opal vs Opalite: The Ultimate Guide to Gemstone Identification

OPAL VERSUS OPALITE

Opals are gemstones that exhibit a play of colors, a phenomenon that occurs when the light diffracts on the silica spheres constituting the stone. Opalite, on the other hand, is a man-made material that mimics the appearance of natural opal.

While the two share a similar name and can be confused, they are vastly different when it comes to origin, chemical composition, and properties.

Definition of Opal and Opalite

Opal is a geological term that refers to a hydrated form of silicon dioxide, which usually contains 3 to 21 percent water by weight. The stone can range in color from white to black, with the most desirable being the ones that show a broad range of play-of-colors, also known as fire.

Opal’s chemical formula is SiO2nH2O, and it belongs to the category of silicates. Opalite, on the other hand, is a trade name for a glassy material made from plastic and the mineral dolomite.

It is occasionally also referred to as sea opal, opal moonstone, or Tiffany stone. The material is produced by melting the plastic and dolomite at high temperatures and allowing it to cool and solidify.

Chemical Composition of Opal and Opalite

Opals contain tiny spheres of silica in their structure, which form in a regular array. The arrangement of the spheres and the size of the voids between them determine how the stone reflects and refracts light.

The stone’s water content, meanwhile, is essential in determining how the spheres pack within the crystal lattice. Opalite, meanwhile, does not contain any naturally occurring crystals.

Instead, it is composed of plastic and dolomite. The plastic that is melted to create opalite is typically made of a form of polystyrene.

History and Usage of Opalite

Opalite was first created in the sixteenth century by artisans in the Murano glassworks of Italy. They used it as a substitute for opal, which was both rarer and more expensive.

The material remained rare until the mid-20th century, when the French company Cristalleries de Sevres began producing it on a large scale. These days, opalite is easily found in craft stores and online, often marketed as a gemstone.

Opalite is often used as an imitation of natural opal. People who cannot afford naturally occurring opal may buy opalite as an alternative.

Some also buy opalite because it is easier to work with than opal.

Differentiating Opal from Opalite

Play of Color

The most significant difference between opal and opalite is the play of colors displayed by opal. Natural opal shows a unique rainbow of colors that are visible depending on the viewing angle.

Opalite, however, does not exhibit this play of colors but reflects a more uniform color.

Hardness

Opal has a hardness of around 5.5-6, whereas opalite’s hardness may vary depending on the plastic used to create it. Most opalites are softer than natural opal, with a hardness range of 5 to 6.

Specific Gravity

Opal has a specific gravity of around 1.98 to 2.25, while opalite’s specific gravity falls in the range of 1.45 to 1.9.

Microscopic Pattern

Under a microscope, opal’s structure is visible in a three-dimensional network of silica spheres that are arranged in a lattice-like pattern. Because opalite is a man-made material, it has a distinct and different microscopic pattern when viewed under the same conditions as natural opal.

Opalite as a Fake Opal

Fake opals refer to any material that is dishonestly presented as natural opal. One common instance of fake opal is when opalite is misrepresented as natural opal.

Misrepresentation of Opalite as Natural Opal

Some sellers may try to pass off opalite as natural opal to unsuspecting buyers. This act is deceptive and dishonest.

Buyers need to understand the difference between natural and synthetic materials to make educated purchases.

Methods for Distinguishing Opalite from Natural Opal

Melting Temperature

A quick and straightforward test to tell the difference between natural opal and opalite is to expose the stone to heat. Since opal’s melting temperature is higher than that of opalite, natural opal will not melt at the same temperature as opalite.

However, this test is not recommended as it could damage the stone or cause the jeweler to lose money.

Hardness

Another method is to test for hardness. Since opalite is typically softer than natural opal, a scratch test can help identify the material.

Gemological Loupe

Using a gemological loupe, trained jewelers can identify the telltale features of natural opal. While opalite may be glossy and attractive, it will not display the same characteristic internal structure as natural opal.

Ultraviolet Radiation

Natural opals will fluorescence under ultraviolet radiation. Since opalite does not possess this feature, jewelers can use a black light to tell opalite from natural opal.

In conclusion, opal and opalite are vastly different in terms of their origin, chemical composition, and properties. While opal is a naturally occurring gemstone with a unique play of colors, opalite is a man-made material created by melting plastic and dolomite.

Buyers who wish to purchase genuine opal should be aware of the origin and chemical characteristics of the stone to avoid being deceived by fake opals.

HOW TO TELL OPAL FROM OPALITE

Opal and opalite are two stones that may look similar at first glance, but they differ vastly in their origin, properties, and value. Opal is a natural gemstone that possesses a mesmerizing play of colors, prized by collectors and jewelry makers alike.

Opalite, meanwhile, is an artificial material made from plastic and dolomite that often imitates the appearance of natural opal. In this article, we will explore how to differentiate opal from opalite using various methods and techniques.

Methods for Differentiating Opal from Opalite

Hardness

The first method to differentiate opal from opalite is through hardness. Opal has a Mohs hardness of around 5.5-6, while opalite is generally softer, with a hardness range of 5 to 6.

This test will require a test kit, which can be purchased from science supply stores or online jewelers. Scratch the surface of the stone with a sharp tool or a knife edge.

If the stone is scratched easily, it is most likely opalite. If the stone leaves a scratch mark on the testing tool, it is most likely opal.

Specific Gravity

The second method is by determining the specific gravity of the stone. Opal has a specific gravity of around 1.98 to 2.25, while opalite’s specific gravity falls in the range of 1.45 to 1.9. To perform this test, the stone is weighed and submerged in a container of water.

The difference between the weight of the stone and the weight of the water displaced by the stone can be used to calculate the specific gravity of the stone.

Refractive Index

The refractive index is the third method to use to differentiate opal from opalite. Natural opal has a refractive index of between 1.44 and 1.46, while opalite’s refractive index ranges around 1.55.

A refractometer can be used to measure the refractive index. The stone is placed on the refractive index tester, and the angle of light emitted from the stone is measured.

The meter reading gives the refractive index value.

Ultraviolet Radiation

The last method to differentiate opal from opalite is through ultraviolet radiation. The majority of natural opal will fluorescence under ultraviolet radiation, while opalite doesn’t possess this feature.

This test requires a UV light source. The stone is placed under the UV light, and the gemologist checks if it fluoresces.

If the stone fluoresces, it is most likely a natural opal.

Comparison of Physical Properties of Opal and Opalite

Visual Appearance

Opal is a colorful gemstone that displays a unique play of colors in various patterns and hues. Opalite, however, is a milky white or clear glassy material, and it’s often used as a substitute for natural opal.

Magnification

Under magnification, natural opal typically exhibits a rock-like surface with a distinctive pattern that looks like hexagonal shapes. On the other hand, opalite will display a more uniform and artificial pattern that is not present in natural opal.

Heat Sensitivity

Opal has a low melting point due to its high water content, and it can crack or melt under high temperatures. Opalite, on the other hand, is resistant to heat.

Comparison of Physical and Chemical Properties of Opal and Opalite

Appearance

Natural opal has a range of colors, including white, black, red, orange, green, yellow, and blue, depending on the exact composite elements. The stone usually displays play-of-colors, which is a phenomenon where the colors interact with the surrounding light source.

Opalite, being man-made, is a white or colorless glassy material with no play-of-colors.

Specific Gravity

Opal has a higher specific gravity compared to opalite. This is because opal contains a higher percentage of water.

The specific gravity of opal ranges from 1.98 to 2.25 g/cm, while opalite ranges from 1.45 to 1.92 g/cm.

Heat Sensitivity

Natural opal is highly sensitive to heat and susceptible to damage, even cracking at higher temperatures. However, opalite is artificial and produced at high temperatures, making it more heat-resistant.

Hardness

Opal has a lower level of hardness compared to opalite. Opal sits at 5.5-6 on the Mohs scale of hardness, while opalite is softer, ranging from 5 to 6.

Refractive Index

Natural opal and opalite have significantly different refractive indices. The average refractive index of natural opal is between 1.44-1.46, while opalite has a higher refractive index of around 1.55.

Fluorescence

Only natural opal typically fluoresces under ultraviolet radiation. Opalite doesn’t possess this trait, which is a significant factor in differentiating the two stones.

Summary of Differences Between Opal and Opalite

Natural opal is a sought-after gemstone that displays a play-of-colors that appears to shift as the viewing angle changes. Opal is a hydrated form of silicon dioxide that is typically found underground and must be mined.

On the other hand, opalite is a man-made material that is made from plastic resin and dolomite. It is widely used as a substitute for natural opal given the high cost of the latter.

In conclusion, while opal and opalite may look similar, they differ significantly in origin, physical and chemical properties, and value. Understanding how to differentiate them is crucial to making an informed decision when purchasing gemstones.

CONCLUSION

In summary, opal and opalite are two gemstones that differ greatly in their origin, properties, and composition. Opal is a naturally occurring gemstone that is prized for its mesmerizing play of colors while opalite is an artificial material that is created by melting plastic and dolomite.

Though they may appear similar at first glance, the two stones have distinct differences that can be observed and identified using specific methods.

Understanding the Chemical Composition

Opal is composed of hydrated silicon dioxide with a chemical formula of SiO2.nH2O while opalite is made up of plastic and the mineral dolomite. Opal contains a high percentage of water which is crucial to the stone’s formation, while opalite contains no water in its composition.

Play of Color

The play of colors is a characteristic unique to opal. The colors observed depend on various factors such as the angle of light, composition, and crystal structure.

In contrast, opalite is usually milky white or clear and does not display any play of colors.

Identification Methods

Several methods can be used to differentiate opal from opalite. These identification methods include hardness, specific gravity, refractive index, magnification, heat sensitivity, and ultraviolet radiation.

Each of these methods can provide valuable clues to determine the origin of a gemstone.

Importance of Accurate Identification

It’s crucial to differentiate between opal and opalite because they have vastly different values. Opal is a rare and highly valuable natural gemstone, while opalite is an artificial material produced on a large scale.

Knowing how to identify each stone accurately is essential when making an informed purchase or sale. It’s also essential for collectors and appraisers to be able to identify the real value of each stone precisely.

In conclusion, opal and opalite are two gemstones that may appear similar but differ widely in physical and chemical properties. Understanding the characteristics of natural opal and opalite is vital to accurate identification and valuation.

Using a combination of various methods, such as refractive index, specific gravity, and magnification, can help in determining whether a gemstone is natural opal or opalite. Overall, the scientific classification and identification of natural opal need careful consideration of its origin, composition, and structure, making it one of the most enthralling and fascinating gemstones in the world of mineralogy.

In conclusion, differentiating opal from opalite requires an understanding of their unique properties, including chemical composition, play of color, and identification methods. It is essential to accurately identify each stone to avoid falling victim to scams and to determine their true value.

By using various methods and techniques to distinguish between natural opal and opalite, one can make educated decisions when buying, selling, or collecting gemstones.

FAQs:

1.

What is the difference between opal and opalite? Opal is a naturally occurring gemstone with a unique play-of-colors, while opalite is an artificial material made from plastic and dolomite that often imitates the appearance of natural opal.

2. How do you differentiate opal from opalite?

Methods for distinguishing the two include testing for hardness, specific gravity, refractive index, magnification, heat sensitivity, and ultraviolet radiation. 3.

What is the play of colors in opal? The play of colors is a phenomenon unique to opal where it displays a range of colors that appear to shift as the angle of the light changes.

4. What is the chemical composition of opal?

Opal is composed of hydrated silicon dioxide with a chemical formula of SiO2.nH2O. 5.

Why is accurate identification of opal important? Accurately identifying opal is important to determine its true value and avoid falling victim to scams.

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