English: Quartz

Silicon dioxide / Cuarzo / Cuarzo

Silicon dioxide (SiO₂) = quartz (the; Old Slavic tvrudu, "hard", or Middle High German querch, "dwarf");

Mineral occurring as the main constituent of numerous types of rock, made of crystallized anhydrous silicon dioxide, consists of 6-sided regular prisms with attached, regular pyramids when growing freely, belonging to the trigonal class. Quartz is sometimes confused with calcite, but can be easily distinguished by its greater hardness, lower birefringence and the reaction of calcite with dilute hydrochloric acid.

Colorless, transparent rock crystals correspond to all quartz varieties
is closest to the theoretical chemical composition of the formula SiO2 (practically pure silicon dioxide).

Milky white crystal types can contain various quantities of gaseous, liquid and solid components as mechanical admixtures.

Inclusions of tiny crystals of rutile, actinolite, hematite and other minerals are also possible in rock crystals.

The incorporation of foreign ions into the quartz structure is only possible to a limited extent (these structural defects then form color centers that cause idiochromatic (self-colored) color varieties, e.g. amethyst, citrine, smoky quartz, rose quartz.

Rock crystal is available in huge crystals up to over a meter in size.
meters as well as in the tiniest dimensions.

Rock crystals are individuals, they were "born" and they grew.
Their appearance was influenced by the environment (temperature, pressure, fellow solvents, degree of saturation of the solution) in which they formed.
There are hardly any two individuals that are completely identical in size, formation, color and clarity.
Show rock crystals:

*** different habitus (shape) such as:
isometric, short or long prismatic, columnar, acicular, thin or thick tabular, pyramidal, transitional, steeply hombohedral (Ticino), trigonal, Dauphinér, Muzo, Bamberg.

*** different tracht (all surface combinations of the crystal).

*** different parallel legal adhesions
( e.g. sceptre quartz).

*** Different symmetrical, lawful intergrowths (twins or intergrowths).

*** Different growth disorders (due to changes in pressure, temperature, solutions).

*** different shape varieties such as knife quartz, thread quartz, phantom quartz, cactus quartz, fortress quartz, sprout quartz, artichoke quartz, window quartz, star quartz, comb quartz, skeleton quartz, cap quartz, and many more