Quartz

Quartz is the second-most-abundant mineral in Earth's continental crust, after feldspar. Its crystal structure is a continuous framework of SiO₄silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO₂.

There are many different varieties of quartz, several of which are semi-precious gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Europe and the Middle East.

Etymology

The word "quartz" is derived from the German word "Quarz" and its Middle High German ancestor "twarc", which probably originated in Slavic, cf. Czech tvrdý ("hard"), Polish twardy ("hard"), Serbian and Croatian tvrd ("hard").

The Ancient Greeks referred to quartz as κρύσταλλος (krustallos) derived from the Ancient Greek κρύος (kruos) meaning "icy cold", because some philosophers (including Theophrastus) apparently believed the mineral to be a form of supercooled ice. Today, the term rock crystal is sometimes used as an alternative name for the purest form of quartz.

Crystal oscillator

A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a precise frequency. This frequency is commonly used to keep track of time, as in quartz wristwatches, to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits incorporating them became known as crystal oscillators, but other piezoelectric materials including polycrystalline ceramics are used in similar circuits.

Quartz crystals are manufactured for frequencies from a few tens of kilohertz to hundreds of megahertz. More than two billion crystals are manufactured annually. Most are used for consumer devices such as wristwatches, clocks, radios, computers, and cellphones. Quartz crystals are also found inside test and measurement equipment, such as counters, signal generators, and oscilloscopes.

Quartz (publication)

Quartz (qz.com) is a global digital-only business news publication. It is owned by Atlantic Media Co., the publisher of The Atlantic, National Journal, and Government Executive. Its team of 150 staff members was pulled together from prominent brands in business journalism: Bloomberg, The Wall Street Journal, The Economist, and The New York Times." The four initial sponsors of Quartz were Boeing, Chevron, Cadillac, and Credit Suisse. Quartz's core market is global business people, with its focus on international markets. Its news articles cover global economy news, ranging from geo-political conflicts to policies and regulations.

History

Name

The name "Quartz" was chosen for various reasons. The name "Quartz" is named after a type of mineral that can be found all over the world and contributed to intense geological activity. The ability of this mineral would then associate with the brand identity, creating new brand's character: global, disruptive and digital. Furthermore, "Quartz" contains two of the rarest letters in English Language, Q and Z, making it a special-looking word. When referring to the Quartz publication website, they took off all the ordinary characters leaving behind qz.com, making it a distinctive website. Also, the fact that there are fewer letters to type into a small mobile keyboard makes it a more user-friendly website.

Spiral

In mathematics, a spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point.

Spirals and helices

Two major definitions of "spiral" in a respected American dictionary are:

Definition a describes a planar curve, that extends in both of the perpendicular directions within its plane; the groove on one side of a record closely approximates a plane spiral (and it is by the finite width and depth of the groove, but not by the wider spacing between than within tracks, that it falls short of being a perfect example); note that successive loops differ in diameter. In another example, the "center lines" of the arms of a spiral galaxy trace logarithmic spirals.

Definition b includes two kinds of 3-dimensional relatives of spirals:

Spiral (disambiguation)

A spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point.

Spiral may also refer to:

Science, mathematics and art

Computer science

Transport

Film and television

List of Mini-Cons

This is the list of all known Mini-Cons from the Transformers toy line and other series.

Armada

Partnered Mini-Cons