13 Quartz Crystal

Quartz is likely one of the most common minerals you will come across while out collecting. It is a very abundant mineral in the continental crust and it is both physically and chemically stable, which means it can accumulate at the surface, while other minerals and rocks weather away.

 

CHEMICAL FORMULA - SiO2 (Silicon Oxide or Silicon Dioxide)

CRYSTAL SYSTEM - Trigonal or Rhombohedral (3 axes of equal length and 120 degrees apart, in one plane; and

a 4th axis perpendicular to the plane of the three)

HABIT - 6-sided spear-like crystals, massive See this video www.flickr.com/photos/usageology/52414098179/in/album-721...

 

HARDNESS - 7

LUSTER- Vitreous, waxy

STREAK - white

COLOR - clear, white, brown, black, gray, purple, yellow, pink, blue, green

DENSITY - 3.65

CLEAVAGE - None

FRACTURE - Conchoidal, subconchoidal In this video, the conchoidal fracture is very well exhibited. www.flickr.com/photos/usageology/52414273148/in/album-721...

 

OCCURRENCE – Quartz is a significant component of igneous metamorphic and sedimentary rocks. Quartz crystals often grow in vugs of limestone, that has been penetrated by hot water. Most sand is largely quartz grains.

 

 

 

* It's superior hardness of 7 and lack of cleavage, makes it physically stable. It is hard to wear down, so it tends to stick around on Earth's surface for a long time..

 

* It does not readily react with acids that are found at the Earth's surface, so it is chemically stable.

 

* The most common mineral in sand, whether it be beach sand, dune sand or river sand, is quartz. (If other minerals are dominant it is due to a unique geological situation. As an example, the olivine-rich sand (green sand) beaches of Hawaii arise from the weathering of basalts, due to volcanic eruptions, and the nearly complete absence of quartz on the volcanic islands.) So, other common mineral grains like feldspars, micas, pyroxenes, amphiboles simply weather away leaving the more resistant quartz to accumulate. In terms of Geological age, the older the beach the higher percentage of quartz.

 

* Pure quartz is clear but it can be colored by impurities to quite an astonishing array of colors: white (milky), purple (amethyst), yellowish (citrine), gray or brown to black (smoky), pink (rose quartz). Although very unusual, there is even green quartz and blue quartz.

 

* Quartz can occur in many different forms other than the crystals of #13. Chert, jasper (#5), agate, chalcedony (#5), petrified wood (#10), flint, and even opal (#18) are forms of this ubiquitous mineral.

 

USES:

* Jewelry - Its many beautiful colors and relative hardness make it a desireable inexpensive gemstone.

 

* As a result of its durability, color and abundance, quartz has been used for 1000's of years as a decorative stone.

 

* Major ingredient in glass

 

* Abrasive - sandpaper

 

* Watches and clocks: the rate and regularity at which quartz oscillate helps to keep the time accurate

 

* Electrical & heat insulators

 

* Optical lenses

 

* Sand traps on golf courses

 

We cannot include every detail about the mineral, so here is a Wikipedia link to get you started on exploration: en.wikipedia.org/wiki/Quartz

 

Done