All About Macrocrystalline Quartz-Part 1 The Basics

All About Macrocrystalline Quartz-Part 1 The Basics

Posted by OakRocks on 20th Aug 2021

Quartz has long been the subject of spiritual beliefs and folklore.

We were fortunate enough recently in acquiring a large stock of various Quartzes from several locations and have spent time exploring the online world to better represent them to our customers. We are not metaphysical experts, but many of our customers are. I have decided to share some of what I know, and am learning, with you!

First the scientific stuff: Quartz is a hard, crystalline mineral composed of silica and oxygen. Compared to many other minerals, quartz is chemically very pure, most crystals contain more than 99.5% SiO2. But impurities do occur, causing color varieties. Most Quartz is massive, not crystallized. Crystallization occurs when the silicon dioxide or silica is heated. The source of the heat can be extremely hot water from underground sources, which fills open fissures to create filled quartz veins.

Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. Quartz is found in every continent and probably in every country. It occurs in nearly all igneous, metamorphic, and sedimentary rocks. In America, Arkansas is a notable supplier of beautiful Quartz clusters.

The name Quartz comes from the Saxon word “querklufferz”, meaning cross vein ore. It is believed the word was condensed to 'querertz' and then to 'quertz', and eventually become 'quarz' in German, 'quarzum' in Latin and 'quartz' in English. The name crystal comes from the Greek word krystallos, meaning "ice", as it was believed that rock crystal was water eternally frozen.

There are generally 2 types of quartz: macrocrystalline (individual crystals visible to the unaided eye) and microcrystalline or cryptocrystalline (aggregates of crystals visible only under high magnification). The latter type includes the chalcedony family of agates, jaspers, etc.

In macrocrystalline quartz the fracture surfaces and crystals have a vitreous to resinous luster, often they naturally look polished. But in cryptocrystalline quartz (chalcedony) fractured surfaces are dull.

In most cases macrocrystalline quartz is easy to identify by the following properties:

- hardness: Quartz has a hardness of 7 on the Moh’s scale, it easily scratches glass, and is harder than steel

- glass-like luster (often looks like it is polished)

- poor to indistinct cleavage (meaning it does not break on an even plane)

- conchoidal fracture in crystals, in massive specimens the fracture often looks irregular to the naked eye, but still conchoidal at high magnification.

This blog will concentrate on the Macrocrystalline Quartzes, which include the following varieties:

Milk quartz or milky quartz is the most common variety of macrocrystalline quartz. The white color is caused by minute fluid inclusions of gas or liquid (or both) trapped during crystal formation. These inclusions scatter the light that otherwise would pass through a clear crystal, making this variety opaque.

Other Quartz macrocrystalline varieties tend to be transparent and include:

Clear Quartz, also referred to as Rock Crystal. Optically clear does not mean it has no inclusions. It means that the crystal is not milky or cloudy.

Amethyst, the purple variety, owes its color to traces of iron and aluminum. Though Amethyst is found in America, Africa, Australia, Sri Lanka, Uruguay and Siberia, the largest quantity comes from Brazil.

Citrine is a variety of quartz whose color ranges from a pale yellow, to amber, to light brown due to ferric impurities. Natural Citrine is rare and thus it is generally the most valuable variety of Quartz. Brazil is the leading producer of Citrine. Much of the Citrine on the market is actually heat-treated Amethyst. Citrine was first appreciated as a golden-yellow gemstone in Greece between 300 and 150 BC, during the Hellenistic Age.

Ametrine, also known as Trystine or by its trade name as Bolivianite, is a naturally occurring variety of quartz that is multicolored. It is a mixture of purple amethyst and yellow citrine. Almost all commercially available Ametrine is mined in Bolivia. The color zones visible within Ametrine are due to differing oxidation states of iron within the crystal. The citrine segments have oxidized iron, while the amethyst segments are unoxidized.

Smoky Quartz, the brown, gray or black variety (sometimes called Morion in European countries). The color is caused by natural radiation (in reference to the proximity of other radioactive minerals) or natural irradiation.

Rose Quartz is the pink variety. This lovely color is due to trace amounts of titanium, iron, and manganese in the material. It occurs only in massive form and is found primarily in Brazil or Madagascar. Mineralogists also recognize that there is "Pink Quartz" that actually has been found in crystal formation and gets its very pale pink color form aluminum and phosphorous ions. This variety is very rare and can be quite costly.

Prasiolite, also known as Vermarine, is a variety of quartz that is green in color. Almost all natural Prasiolite comes from one small Brazilian mine. Naturally occurring Prasiolite is also found in Poland and Canada, but it is a very rare mineral in nature; most green quartz is heat-treated amethyst. Hence the commonly used trade name of “Green Amethyst”.

Blue Quartz contains inclusions of fibrous magnesio-riebeckite or crocidolite. Lately I have heard this Quartz referred to as “Blue Rose Quartz”. Dumortierite Quartz is also referred to as Blue Quartz, it has inclusions of the mineral dumortierite within quartz pieces often resulting in silky-appearing splotches with a blue hue. Shades of purple or gray sometimes also are present.

The most ancient record of Quartz known was recorded by Theophrastus in about 300-325 BCE. A n arrowhead carved from Quartz that is estimated to be over 11,000 years old was discovered at the Mount Blakely Dam site in Garland County, Arkansas.

Quartz has long been the subject of spiritual beliefs and folklore. Crystal balls brought back by the Crusaders were believed to possess magical powers. The Ancient Japanese believed quartz formed from the breath of a white dragon and they called clear quartz the “perfect jewel”. They viewed it as a symbol of purity, perseverance, and patience. Indigenous cultures in both North America and Myanmar believe quartzes are living entities.

In addition to a collectible mineral, a decorator rock, or a magical use, Quartz has many industrial uses.

Most notably in the control of radio frequencies. Radios made during World War II had tiny slices of quartz in their tuning circuits. Quartz is also used in watches. Large amounts of quartz sand (also known as silica sand) is used in the manufacture of glass and ceramics and for foundry molds in metal casting. Crushed quartz is used as an abrasive in sandpaper, silica sand is employed in sandblasting, and sandstone (which is composed mostly of quartz) is still used whole to make whetstones, millstones, and grindstones. Silica glass (also called fused quartz) is used in optics to transmit ultraviolet light. Tubing and various vessels of fused quartz have important laboratory applications, and quartz fibers are employed in extremely sensitive weighing devices. It is also used to carve bowls, cups, vases, animals, skulls, and other decorative items.

Quartz crystals can get quite large and may be several feet in length and weigh thousands of pounds. Sometimes quartz forms in such unusual formations that it can be mistaken even with diamond. In fact, there is a variety of quartz named Herkimer Diamonds, found in Herkimer, New York. These quartzes are so named because they form in double terminated or two ended crystals and grow in a diamond-like geometrical shape.

Because there are no specific rules on naming or defining quartz varieties like there are for minerals, the definitions of some quartz varieties and formations are precise and generally accepted, while the definitions of others vary considerably between different dealers or authors. Often times dealers will give Quartz varieties trade names. In addition, there are many different names for formations and shapes of crystals, especially in the metaphysical market. We will explore these in later blogs.

Quartz is also found with various other minerals encased within. These are referred to as inclusions. Desired inclusions include rutilated quartz (included with hairlike inclusions of gold rutile), goethite, gold, pyrite, and tourmaline.

Quartz can have several phenomena including phantom crystals, or asterism (star effect). In my next blog we will discuss various Quartz phenomena and inclusions present in Quartz.

Explore our great selection of  Quartzes here!

You can also find more Quartz available in our Etsy shop here!