Quartz is the most abundant and widespread mineral. An important rock-forming mineral occurs in igneous, metamorphic, and sedimentary rocks. Quartz includes many varieties of gem-quality and ornamental stones and colors. Quartz is piezoelectric and used for accurate timepieces, broadcast emission, and to produce high-intensity halogen lamps in gem-testing devices.

Quartz, gem varieties; quartz gem varieties are citrine, amethyst, rock crystal, rose quartz, smoky quartz, greened amethyst, aventurine, chalcedony, chrysoprase, bloodstone, chrysocolla, tiger’s-eye, varieties of agate, and varieties of chalcedony.

Quartz inclusions; several inclusions have been found in crystalline quartz, also negative crystals, bubbles, cavities, and cracks. Actinolated quartz contains a green needle-like variety of actinolite known as byssolite. Chlorite quartz contains chlorite, which gives a green mossy-like color to quartz. Chrysocolla quartz has blue-green very finely disseminated chrysocolla in quartz. Crocidolite quartz has tiger-eye or tiger’s-eye. Dumortierite quartz is a blue-green very finely disseminated dumortierite in quartz. Goethite quartz contains goethite fibers and crystals, which give quartz a yellow to orange color. Gold quartz is a milk quartz containing very small grains or fibers of native gold. Milky quartz. Hematite quartz has blood-red plates as inclusions in some sunstone or aventurine quartz.

Rutilated quartz has rutile needle inclusions of red, gold color, called Venus’s-hair stone, fléches d’amour and cupid’s darts. When quartz contains needle-like crystals of tourmaline, actinolite, goethite, or other minerals it is known as thetis hair stone. Sagenitic quartz contains any type of needle-like inclusions such as rutile, tourmaline, actinolite, goethite, or other minerals, which sometimes gives a net-like appearance or reticulated needles. Tourmalinated quartz; contains black, or other colored tourmaline. Also spelled tourmalated quartz. Some inclusions such as cracks create an iridescent effect in quartz known as rainbow quartz or iris quartz.

Different Types Of Quartz Crystal
There are six main groups into which crystals can be classified: triclinic, monoclinic, orthorhombic, cubic, tetragonal and hexagonal.

Phantoms
Are when you can see the external crystal shape as a shadow on the inside of a crystal. For example, you can have a quartz crystal and when you view it you can see what looks like quartz crystal shapes on the inside. This is caused by the growth of the crystal. The conditions that cause a crystal to grow may be interrupted. While it is not growing, a layer of another mineral grows over the top of it. Then the main crystal starts to grow again leaving an outline of the initial growth.

Zoning
This is when you can see a single crystal change colors showing what looks like a phantom. Tourmaline is really good at this. You can have a single crystal of tourmaline and when you slice it up you can get a watermelon effect where the outside is green and the inside is pink. Some tourmalines can be sliced and change with each slice.

Enhydro
Many crystals have small water pockets embedded within and have an air bubble that moves, this is called 'enhydro'. Quartz is the most common example, but rainbow obsidian also gets it's color this way with thousands of very small water filled pockets that are stretched out from the flowing of the lava. Once cooled, the pockets of water act as a prism creating the rainbow effect.

Twinnung
Crystals can form in interesting combinations, twining occurs when you have 2 different crystals that form to make one crystal. It can form a sixling that looks like the inside of a bicycle wheel, or as with staurolite it forms perfect crosses.

Cleaning Quartz

Quartz crystals and formations in their natural state can be stained reddish brown from iron, encrusted with clay or coated in tougher minerals like limonite or calcium. With some work and the right techniques and cleaning chemicals you can reveal the sparkling beauty of a crystal.

Initial Cleaning
First you need to remove any clay covering your specimens. For a prize specimen use old toothbrushes, toothpicks, any wooden pointed object. If you have intricate formations or a lot of specimens to clean, try putting them outside in the shade to dry to the point where the clay cracks, then hose with a spray nozzle at maximum force. You will probably need to repeat this process several times, allowing the clay to completely dry between hosing. Make sure all clay is removed before moving on to the next step.

Removing Algae
If your specimen has organic material like algae on it, you can use household bleach to clean it. Rinse well and let it dry for 24 hours before using an acid cleaning method.

Removing Iron Stains
Put the specimens in a plastic bucket and cover them with a preparation of oxalic acid solution. Be aware that too much time in the solution can turn quartz yellow. Let your specimens soak for one to several days.

If staining is very heavy or you want to speed the process along you can heat the solution by standing the bucket in the hot sun. There are some who use an old crock pot instead of a plastic bucket, and heat their acid solution that way. Be sure not to do this indoors because of the toxic fumes the acid puts off. Do not use any type of metal or aluminum container for the acid will create a toxic gas cloud, please remember to use rubber glove and a mask at all times.

When the crystals are clean to your satisfaction, rinse and rinse them again. If you have hard water in your area, it is smart to use distilled water for rinsing to prevent possible yellow staining of the crystals. Soak them in clean water for a day and then allow to dry.

** If the crystals develop a powdery coating as they dry, soak them in a baking soda solution of about 1/3 cup to a gallon of water then rinse well.

Other methods for removing iron stains include: Naval Jelly which contains phosphoric acid and is sold for getting rust off metal but will work on quartz crystals.

Quartzite; a metamorphic rock consisting of a granular, interlocking mass of irregular quartz crystals with irregular boundaries, which are formed from preexisting quartz sandstone or chert. Some samples contains flakes of reddish iron mineral or minute crystals of mica with iridescent effect, which is called aventurine quartz, and frequently contains green chrome-rich mica particles known as fuchsite. If quartzite has a dark-green color due to fuchsite, it is known as quartz schist. Fine-grained, bluish-white quartzite, which is brownish-red veined reportedly comes from Idar, Germany, and contains crystals of pyrite. Found in Russia, Spain, Tanzania, Chile, and India. Also called metaquartzite.