Quartz

People usually gaze into crystals for a glimpse of the future. But in this one, you can see the past. Look for phantoms - ghostly outlines of the crystal\'s former shapes - inside the quartz crystal. Tiny bubbles or mineral grains coated earlier crystal faces that stopped growing. When they started growing again, the coating was trapped, leaving shadowy ghostlike forms inside the crystal.

Quartz

Two thousand years ago, the Greeks looked at quartz and wondered: What is it? They concluded that this clear, hard substance was water frozen so hard it couldn't melt. So they gave it their word for "ice," crystallos-the origin of the word crystal. This photo shows the clear, colorless variety of quartz called rock crystal.

Quartz

Quartz

Quartz crystal/agate cylinder. There are two main groups of quartz: chert and chalcedony. Chalcedony is composed of fibrous crystals intergrown, yielding a variety of patterns including agate. Agate is a variety of chalcedony composed of concentric bands of colors. Agates form in cavities left by gas bubbles in cooling lava. Silica-rich groundwater builds layers of crystals on the cavity walls.

Quartz

There are two main groups of quartz: chert and chalcedony. Chalcedony is composed of fibrous crystals intergrown, yielding a variety of patterns including agate. Agate is a variety of chalcedony composed of concentric bands of colors. Agates form in cavities left by gas bubbles in cooling lava. Silica-rich groundwater builds layers of crystals on the cavity walls.

Quartz

There are two main groups of quartz: chert and chalcedony. Chalcedony is composed of fibrous crystals intergrown, yielding a variety of patterns including agate. Agate is a variety of chalcedony composed of concentric bands of colors. Agates form in cavities left by gas bubbles in cooling lava. Silica-rich groundwater builds layers of crystals on the cavity walls.

Quartz

There are two main groups of quartz: chert and chalcedony. Chalcedony is composed of fibrous crystals intergrown, yielding a variety of patterns including agate. Agate is a variety of chalcedony composed of concentric bands of colors. Agates form in cavities left by gas bubbles in cooling lava. Silica-rich groundwater builds layers of crystals on the cavity walls.

Quartz (Japan Law Twin)

Crystal twins are groups of two or more crystals of the same mineral connected at precise angles. The angles are controlled by the crystal's atomic structure. For example, in a common type of quartz twin, such as in this photo, the crystals join at 84° and 33 minutes.

Quartz (Rutilated)

Quartz (variety: "Bullseye" Agate)

Artificially colored, cut and polished stone.

Quartz (variety: "Landscape" Agate)

Sometimes, agate grows in such a way that it looks like a painted landscape. Notice how this specimen appears to have a photo of the sunset, behind trees?

Quartz (variety: Agate)

Agate is the concentrically banded variety of chalcedony, which is, in turn, actually tiny fibrous crystals of quartz. The quartz crystals in agate is said to be cryptocrystalline - which means that it has a crystalline structure so fine that no distinct particles are recognizable by the naked eye, nor under the microscope, with regular magnification. The quartz fibers form vertical to the surface of other layers, forming the banded structure. Bands can be of the same color, or of a variety of colors, as shown in this specimen. Agate forms in cavities left by gas bubbles in cooling lava. Silica-rich groundwater builds layers of crystals on the cavity walls.

Quartz (variety: Agate)

Agate is the concentrically banded variety of chalcedony, which is, in turn, actually tiny fibrous crystals of quartz. The quartz crystals in agate is said to be cryptocrystalline - which means that it has a crystalline structure so fine that no distinct particles are recognizable by the naked eye, nor under the microscope, with regular magnification. The quartz fibers form vertical to the surface of other layers, forming the banded structure. Bands can be of the same color, or of a variety of colors, as shown in this specimen. Agate forms in cavities left by gas bubbles in cooling lava. Silica-rich groundwater builds layers of crystals on the cavity walls.

Quartz (variety: Agate)

Amethyst replacing dinosaur bone.

Quartz (variety: Amethyst)

Resembling a monarch's scepter, this type of growth oddity is called scepterism. This specimen shows amethyst-topped rock crystal quartz. This happens when a second crystal (the amethyst) grew on top of the clear rock crystal after the rock crystal has stopped growing. The different color exhibited by the cap indicates secondary growth development. It due to different conditions, temperature, and chemical content of the environment upon which the two crystals formed.

Quartz (variety: Amethyst)

A geode is a nodule of stone having a cavity lined with crystals or mineral matter. It may look like a piece of insignificant rock on the outside, but when cut open, it usually contains a myriad of crystals (typically amethyst or rock crystal) on a bed of chalcedony. This specimen shows a cross section of a geode lined with amethyst quartz.

Quartz (variety: Amethyst)

Of all quartz varieties, amethyst is the most prized. According to Roman mythology, amethyst was colored purple by Bacchus, the god of wine, and was thought to offer protection from intoxication. The gem derives its name from the Greek word meaning "not to intoxicate." It is now known that just a few iron atoms replacing some of the silicon in quartz causes the purple color. Natural radiation from surrounding rocks where the quartz crystals grew changed these impure atoms into a special form of iron (Fe+4) that absorbs all colors of light except blue and red, which are reflected back to our eyes, giving rise to amethyst's purple color.

Quartz (variety: Amethyst)

Quartz (variety: Amethyst) coating calcite

Sometimes crystals of one mineral grow on top of crystals of a different mineral, producing an overgrowth. In most cases, you can still see the shape of the crystals that were overgrown, even though they may have been completely covered or dissolved. This specimen shows amethyst growing over calcite crystals.

Quartz (variety: Rock Crystal)

Two thousand years ago, the Greeks looked at quartz and wondered: What is it? They concluded that this clear, hard substance was water frozen so hard it couldn't melt. So they gave it their word for "ice," crystallos-the origin of the word crystal. This photo shows the clear, colorless variety of quartz called rock crystal.

Quartz (variety: Rose Quartz)

This specimen is sometimes called the "Pink Tutu" because of its rose quartz frill. The smoky quartz formed first, then the rose quartz. Geologists suspect the pink tint comes from traces of aluminum and phosphorus.

Quartz (variety: Smoky Quartz)

These two gem-quality crystals have the six-sided pencil shape typical of quartz. Together, they weigh a whopping 52.6 kg (117 lbs). If you look closely, you can see smaller crystals growing on their surfaces.

Smoky Quartz on Microcline

Pegmatites are exceptionally coarse-grained rocks born of molten rock, or magma, beneath the Earth's surface. They produce many of the crystal giants of the mineral kingdom. Over 300 minerals come from pegmatite deposits. Some of these minerals are extremely rare, form exquisite gem-quality crystals, are found only in pegmatites, and provide important industrial materials. This growth of smoky quartz and microline is just one example of the diversity and beauty of the crystals that form in pegmatites.