How to test quartz hardness and luster?

What is quartz?

Quartz is considered one of the most abundant minerals found in the Earth crust that comes second in abundance after feldspar. The term ‘Quartz’ is derived from the Polish words “Twardy” and “kwardy” meaning ‘hard’.

It is generally a chemical compound that consists of two parts of oxygen and one part of silicon referring it to be a silicon dioxide SiO2. Quartz is considered to be one of the most useful substances due to its finest and unique properties.

Where is quartz found?

Quartz is widely distributed and one of the most abundant minerals that are present in plentiful amounts in all parts of the world. It can be formed at all temperatures.

It is abundant in metamorphic, sedimentary and igneous rocks. Quartz is highly resistant to both chemical and mechanical weathering.

This feature of the durability of quartz makes it a primary constituent of the river, desert sand and beach and it also makes it the dominant mineral of mountain tops as well.

Quartz is basically durable, plentiful and ubiquitous, and its minable deposits are found all around the world. This will be no surprise if you consider that nearly all the sand on earth is made up of grains of quartz.

Types of quartz

Quartz comes in a variety of forms on the planet. Some of the common types of quartz are known as ametrine, onyx, smoky quartz, amethyst, milky quartz, agate, jasper, and so much more.

Geologists and mineralogists identify different types of quartz to use for specific purposes.

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Uses of quartz

Quartz is a beneficial mineral, and that can be linked to its enormous beneficial chemical properties. It is considered to be a very durable mineral and is chemically inert with most substances when it comes into contact with them.

The heat resistance and electrical properties make it valuable to be used in electronic products. For many decades, quartz has been used in the making of bath and kitchen counterparts.

Quartz is one of the top countertop materials that is purchased among contractors, homeowners and builders alongside granite and marble.

What is luster?

Luster is described as the way minerals reflect light off their surface.

Special terms are used by the mineralogists to define luster, and it is considered one of the most important characteristics that need to be recognized for the identification of mineral.

One simple way to define luster is based on the property of mineral being non-metallic or metallic. Minerals that are shiny and opaque such as pyrite have a metallic luster.

On the other hand, minerals that do not look like metals such as quartz have non-metallic luster.

Luster is one of the essential characteristics that are important to identify the required mineral. Just like color, density, hardness, streak, cleavage and fracture holds primary importance in identifying minerals, luster of the mineral should never be taken for granted.

How to test the luster of quartz?

Luster is basically how a mineral reflects light, but it shouldn’t be confused with the color of the mineral as both (luster and color) are used generally to describe the appearance of mineral.

Luster should only be specified to the terms generated by mineralogists based on their metallic and non-metallic features. Let’s have a look at six types of non-metallic luster that would help and guide you towards testing your mineral:

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Non-metallic luster Appearance
Adamantine Sparkly
Earthy Dull, clay-like
Pearly Pearl-like
Resinous Like resins, e.g. tree sap
Silky Soft-looking with long fibers
Vitreous Glassy

 

Looking at the table, you can easily identify the minerals based on their appearance. Diamond has a sparkly appearance so it can easily be categorized as an adamantine luster. Quartz is not sparky and has a glassy, vitreous luster. Sulphur has resinous luster as it reflects less light than that of quartz.

Why is the hardness test for mineral important?

Testing the hardness of a mineral is all about testing its resistance to scratching. The hardness is controlled by the atomic bonds strength within the minerals. After determining the luster of a mineral, hardness is considered one of the most important tests for identifying a mi

neral. A hardness test gives you a detailed view regarding the suitability of specific material in industries and other purposes. Hardness also helps the geologists to identify some minerals while doing their fieldwork in addition to telling them about the composition of minerals.

How to test the hardness of quartz?

By testing the hardness of the quartz, we mean to be measuring how much it resists to be scratched or being cut instead of measuring the force needed to break it.

Take an example of glass! If we try to scratch the glass with the point of the nail, the glass won’t get scratched because it is harder than the nail. But to measure how much harder it is, we need some specific scale to measure the hardness.

Geologist Friedrich Mohs developed the Moh’s hardness scale in 1812 that has been used to identify the hardness of minerals for years. This scale lists the minerals on the base of its standard hardness ranging from 1 (softest) to 10 (the hardest).

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Mineral Hardness
Talc 1
Gypsum 2
Calcite 3
Fluorite 4
Apatite 5
Orthroclase 6
Quartz 7
Topaz 8
Corundum 9
Diamond 10

 

Some common objects were also identified for their hardness. These are:

  •  Fingernail-  2.5
  • Copper penny-   3
  • Iron nail-  4
  • Glass-        5

Moh’s scale has already identified the relevant standard hardness of quartz so the hardness test can be used to identify the hardness of other unidentified specimen or minerals or simply to identify the mineral (quartz) itself.

Materials

  • A glass jar
  • Your fingernail
  • Piece of copper pipe or several pennies
  • Several unidentified mineral specimens
  • Several identified mineral specimen
  • An iron nail

Procedure

You can start by testing quartz by scratching it with glass.

A polished round piece of quartz won’t do the work so it’s better to have a piece that is edgy that can scratch the glass. You need to hold the glass firmly and try to make a scratch by pressing the point of quartz.

Press it a little harder than you would do while drawing with a pencil. You need to remember that you just aim at making a scratch to the glass and not breaking it. You will hear a grating sound when you made a scratch on the glass.

The scratch will not rub off when you rub your finger over the scratch. Quartz will definitely scratch the glass because its hardness is greater than the glass. You can try this procedure with various minerals using some common materials such as iron nail and fingernail to confirm the identification of these minerals.

Safety

The mineral specimen should be handled with great care because they can be as sharp as broken glass. While identifying the minerals using hardness tests, you should be very careful not to damage the expensive or delicate specimen.

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