What is the softest mineral called?

What is talc? Talc is a silicate that has a layered structure, is greasy to the touch and has a pronounced pearlescent luster. It has a white color with various shades, which are determined by the impurities included in the composition (nickel, manganese, chromium, iron and aluminum). The intensity of the color is determined by the degree of purification. Depending on the structure and existing impurities, the following types of talc mineral are distinguished:

1. Agalite. It has a needle-like structure. The crystal fibers are located almost parallel, in the same direction.
2. Minnesotaite. The presence of iron (it replaces magnesium) gives it a brownish tint.
3. Steatite. Characterized by a dense structure. It is also called wen.
4. Willemseit. Due to the presence of nickel, it has a bluish or greenish tint.
5. Noble talc. A translucent stone with high density. Well processed.
6. Soapstone chlorite. Contains chloride.

According to the degree of grinding, talc powder, microtalc and coarse grinding are distinguished. It has a standard hardness of 1. That is, it is the softest mineral. It was first discovered and described by Michael Faraday while studying dielectrics. It is mined in America, Canada, China, France and other countries. In Russia, the largest deposits are located in the Urals and Krasnoyarsk Territory.

Properties of the mineral

Not everyone knows what talc is and what its physical and chemical characteristics are. It is a chemically complex composition of hydrogenated magnesium silicate. The approximate chemical formula of talc looks like this: Mg3Si4O10(OH)2. It may vary slightly due to the replacement of some impurities with others. We list the main properties of talc:

1. Odorless.
2. Does not dissolve in water.
3. It does not react chemically with acids and settles to the bottom of the container.
4. It is a good adsorbent. Perfectly absorbs moisture and odors.
5. Has poor thermal conductivity.
6. Characterized by low hardness equal to 1.
7. It has a low density (2,75 kg/m³). It has no jewelry value.
8. Fireproof. When heated strongly (800-900°C), it turns into a very solid substance.
9. Has good dispersibility. Finely ground powder forms a suspension with water.
10. Is a dielectric.

It is also credited with magical properties. The powder was used for all kinds of potions designed to restore youth and beauty. These were mainly creams and poultices made with talcum powder. The stone has positive energy. It is very useful to keep solid talc products in the house.

This mineral has been used by mankind since ancient times. Ancient craftsmen used it quite widely because of its softness and easy workability. Even in Ancient Egypt, amulets and necklaces were made from it. Russian stone cutters made icons. In China, colored talc was passed off as valuable jade. The Sumerians carved seals.

Areas of use

What is talc and what is it used for? Let’s look at the most famous areas:

1. In medicine. As a powder for the treatment of bedsores and skin diseases. It is also used as a binder in tablets.
2. In technology. Used as a solid lubricant and as an additive for motor oils.
3. In the food industry. It is used to sprinkle chocolate products, and it is used to make molds for the production of liqueur candy shells. Food grade talc has a code – E553b.
4. At home. Various rubber products (gloves, shoes, etc.) are sprinkled with it to prevent sticking.
5. In construction. They are used for cladding bathrooms and saunas, and also as stones for stoves.
6. In cosmetology. It is used to produce baby powder, liquid body talc and massage powder.

Let us analyze the use of talc in cosmetology and dermatology in more detail. It has been finding its consumers for more than 100 years and is still an indispensable component of many cosmetics. As the softest mineral, it is most often used in powder form. It is definitely included in powder and eye shadow. Scented talc is used as a deodorant and applied to areas of increased sweating. Using it during the depilation procedure prevents ingrown hairs. Liquid talc is very effective in caring for rough heels. It is added to shaving cream because it promotes easy glide. It is due to this quality that talc powder is used for massage.

What is talc? The first thing that comes to mind for many is baby powder. Good absorbency makes it suitable for children. It also has anti-inflammatory properties. Used to treat and prevent heat rash in infants. Talc is the main component of powder. In addition, the composition includes extracts of medicinal plants, zinc oxide and starch.

Pure ground talc is sold in pharmacies. Release form: powder for external use. Available in jars and small bags.

When working with talc, you need to be careful and try not to inhale it. There is even an occupational disease – talcosis, which is usually detected in mining workers and medical personnel. Without constant contact with the powder, it is impossible to acquire this disease.

The Mohs hardness scale is an international scale for determining the relative hardness of a mineral, invented by Friedrich Mohs in 1811. It has ten levels of hardness, with the first level being the softest material and the tenth being the hardest. For each level, a reference mineral is selected, and the assessment is carried out by scratching the test mineral with a standard. In addition to the ten basic levels, there are also intermediate ones: if the mineral being tested is scratched by a standard with a hardness of 5 and at the same time leaves scratches on a standard with a hardness of 4, then it is assigned a hardness level of 4.5.

It must be remembered that the Mohs scale evaluates the relative, and not the absolute, hardness of a mineral. This means that a mineral of the eighth level will not be twice as hard as a mineral of the fourth level, and that between different levels there may be intervals of real hardness of different “lengths”. For example, the second and third Mohs levels in absolute numbers are 3 and 9, respectively (a difference of 3 times and 6 units), and the third and fourth are 9 and 21 (a difference of approximately 2 times and 12 units). Absolute hardness is measured with a sclerometer (which is essentially just a scratching instrument with clear characteristics). At the same time, the tenth Mohs level has 1600 absolute hardness units.

Characteristics of soft minerals from the Mohs scale

Soft minerals score below seven on the Mohs scale. Let’s look at the reference samples of each level as an example, putting the softest mineral at the beginning of the list.

• Talc (hardness level 1, scratchable with a fingernail). It is a mineral from the silicate class, dense, layered, somewhat greasy to the touch, with a faint color (most often gray, white or pale pink). Under pressure, impact and any other mechanical impact, even minor, it turns into powder.
• Plaster (hardness level 2, scratchable with a fingernail). The most common mineral is white, but other shades are also found – grayish, brownish, reddish, and occasionally yellowish.
• Calcite (hardness level 3, scratchable with a copper coin). A rock-forming mineral whose chemical composition is calcium carbonate. It forms the basis of limestone, chalk and marble, and is found in large quantities in the shells and skeletons of various invertebrates. Usually white or colorless, but due to iron and nickel impurities it can take on a faint pink, brown or green tint.
• Fluorite (hardness level 4, easily scratched with a knife or glass), also known as fluorspar. A fragile mineral with a wide range of colors: it can be purple, green, pink, red or colorless.
• Apatite (hardness level 5, difficult to scratch with a knife or glass). In nature, it occurs in the form of prismatic crystals of delicate shades – green, yellowish-green, blue, pink.
• Orthoclase (hardness level 6, scratches with a file and scratches glass). It belongs to rock-forming silicates; from a chemical point of view, it is potassium feldspar. Found in granites and pegmatites.

Other soft minerals

Soft minerals are not limited to the above list. All reference examples have analogs in hardness. For example, the hardness of talc is characteristic of graphite and molybdenite, mica and chlorite are similar to gypsum, amber and serpentine are similar to calcite, pearls and dolomite are similar to fluorite, turquoise and lapis lazuli are similar to apatite, pyrite and opal are similar to orthoclase.

However, one must understand that many soft minerals do not have such a clearly defined hardness as the reference ones. This is due to the fact that they can change their hardness coefficient depending on external factors, for example, the state of aggregation or variety. Pearls are indeed on average statistically close to fluorite in hardness, but they can be softer than four (level 3 in pearls is very common). Similarly, amber can have a hardness of up to two, inclusive, and soapstone, which is equivalent to talc and is by default considered a mineral with a hardness of the first level, in some cases can have a hardness of up to five.

Despite the fact that on the Mohs scale level 10 is considered the maximum, and level 1 the minimum, there are also values ​​that go beyond these limits. Rubidium is considered the softest mineral in the world (Mohs hardness 0.2-0.3); cesium has approximately the same hardness. Since the Mohs index of rubidium and cesium fluctuates (which is normal for most substances outside the reference values), it is technically impossible to determine which mineral is the softest. Lithium, sodium and potassium are also much softer than talc with its “one” – their hardness averages 0.5-0.6.

How to identify soft minerals

The division into soft and hard minerals according to Mohs is carried out along the border where the stone ceases to be scratched by improvised materials and can only be damaged by specialized objects. The above soft minerals are marked, in addition to the level of hardness, by the main object affecting them – some are scratched with copper, and some only with a knife or file. Hard minerals can only be scratched by something specific, such as a diamond.

Scope of application of soft minerals

• Talc. Talc powder has a fat content, like the mineral itself, and is used where it is necessary to prevent too close contact of surfaces and their friction. For example, most rubber industry products are sprinkled with talc so that they do not stick together upon contact and do not wear out. This method is used in everything from rubber gloves to bicycle tires. In addition, talc is present in dietary supplements, tablets and cosmetics.
• Gypsum. Burnt or heated gypsum powder, diluted in water, has a very rapid setting and hardens instantly. All uses of this mineral are tied to this property. Gypsum is used in medicine to fix fractures; it is used to make various decorative objects (figurines, sculptures), as well as non-strength elements of building structures (cornices, rosettes).
• Calcite. It is found in many commonly used minerals (such as chalk and limestones), but the best known variant is marble, which is made entirely of calcite. And marble is used everywhere: from the manufacture of decorative and household items (such as figurines, paperweights or writing instruments) to sculpture and cladding of architectural objects.
• Fluorite. Translated from Latin, it is called “fluid”, since since ancient times fluorite has been used in metallurgy to produce low-melting slags. Its second known use is also associated with the melting process – hydrofluoric acid, also known as hydrofluoric acid, largely consists of fluorite. This acid is used to melt and dissolve glass.
• Apatite. Transparent and translucent apatite crystals are used in jewelry, most often as a frame for other stones – apatite is a fairly fragile mineral, and in addition, the size of its crystals is small. In addition, apatite is a valuable raw material for the production of phosphorus and its derivatives (for example, phosphoric acid and phosphate fertilizers). A significant amount of mined apatite goes into industry – ferrous and non-ferrous metallurgy, for the production of ceramics and glass.
• Orthoclase. This mineral is the basis for most types of ceramics. All electroceramics are made using orthoclase, which is also an important element in the production of high-quality porcelain. A rare transparent type of orthoclase (adularia) is used in jewelry.
• Other soft minerals. In addition to the listed standard minerals, those similar in hardness are also used in various fields of production. Some are used as elements of jewelry or ornamental stones, they are inserted into jewelry, figurines or small decorative objects are cut out of them – figurines, ashtrays, boxes. The most famous in this area are opals, turquoise, corals, amber, and malachite. Others are important elements in technology – for example, mica is used for Geiger counters, and as an electrical insulating material in aircraft engineering, and in the glass industry for the manufacture of optical glasses. Still others have long been used in construction, especially granite (analogous to orthoclase in hardness), which is used to line walls, pave floors, and is used to create architectural decor, and is used as a material for monuments.

Conclusion

Minerals considered soft on the Mohs scale vary widely in appearance, chemical composition, and uses. They participate in all spheres of human life – in metallurgy, in the chemical industry, in architecture, and in jewelry.