Aragonite

Aragonite usually forms short to long prismatic crystals but also forms fibrous acicular, columnar, and stalactitic aggregates.

Aragonite

This specimen grew on a cave wall. These aragonite formations were named by miners working in Australian iron mines. They are known as "flos ferri," Latin for "flower of iron."

Aragonite with goethite

This specimen illustrates the typical spiked crystal shape of aragonite. Aragonite usually forms short to long prismatic crystals but also forms fibrous acicular, columnar, and stalactitic aggregates.

Azurite

Bisbee, Arizona is famous for the diversity and magnificance of the minerals mined there. Over two hundred minerals have been found there. Most prominent among the Bisbee minerals are azurite, malachite, and other copper minerals. This specimen of azurite came from the famous Copper Queen Mine in Bisbee.

Azurite

Bisbee, Arizona is famous for the diversity and magnificance of the minerals mined there. Over two hundred minerals have been found there. Most prominent among the Bisbee minerals are azurite, malachite, and other copper minerals. This specimen of azurite came from the famous Copper Queen mine in Bisbee.

Azurite

Bisbee, Arizona is famous for the diversity and magnificance of the minerals mined there. Over two hundred minerals have been found there. Most prominent among the Bisbee minerals are azurite, malachite, and other copper minerals. This specimen of azurite came from the famous Copper Queen mine in Bisbee. The chemical composition of azurite is Cu3(CO3)2(OH)2.

Azurite

The name azurite is taken from the characteristic azure-blue color of the mineral. It is an ore of copper and a minor ornamental stone. Azurite commonly occurs with the minerals malachite, limonite, and chalcopyrite. Crystals are usually well-formed equidimensional or tabular, but can also occur as radiating, botryoidal, or incrusting crystals. This specimen is from the Copper Queen Mine in Bisbee, AZ.

Azurite

The name azurite is taken from the characteristic azure-blue color of the mineral. It is an ore of copper and a minor ornamental stone. Azurite commonly occurs with the minerals malachite, limonite, and chalcopyrite. Crystals are usually well-formed equidimensional or tabular, but can also occur as radiating, botryoidal, or incrusting crystals. This specimen is from the Copper Queen Mine in Bisbee, AZ.

Azurite altering to malachite

This photo shows a very large single crystal of azurite (intense azure blue) just starting to alter to malachite (green) on its surface. If the new mineral retains the crystal shape of the original, the specimen is called a pseudomorph - meaning "false form." The original crystal of azurite is unstable in open air and most likely reacted with carbon dioxide or water in the air to alter to green malachite.

Azurite with Malachite

Bisbee, Arizona is famous for the diversity and magnificance of the minerals mined there. Over two hundred minerals have been found there. Most prominent among the Bisbee minerals are azurite, malachite, and other copper minerals. This group of large (3.5cm high) azurite crystals came from the famous Copper Queen mine in Bisbee.

Calcite

Calcite has been found in over 2,500 distinct shapes. No one is quite sure why there are so many varieties of calcite, but impurities, temperature and composition during growth all may create variations on basic shapes. There are three basic shapes: trigonal prism, scalenohedron, and rhombohedron. The crystals shown here are referred to as triple dogtooth, a grouping of thick scalenohedral crystals that are double pyramid in form. The point of the scalenohedron is sharp and resembles the canine tooth of a dog, hence the name.

Calcite

Calcite has been found in over 2,500 distinct shapes. No one is quite sure why there are so many varieties of calcite, but impurities, temperature and composition during growth all may create variations on basic shapes. There are three basic shapes: trigonal prism, scalenohedron, and rhombohedron. The crystals shown here are hexagonal tabular crystals.

Calcite

Calcite has been found in over 2,500 distinct shapes. No one is quite sure why there are so many varieties of calcite, but impurities, temperature and composition during growth all may create variations on basic shapes. There are three basic shapes: trigonal prism, scalenohedron, and rhombohedron. The crystals shown here are rhombohedron.

Calcite

This calcite is a forced twin crystal.

Calcite

Calcite has been found in over 2,500 distinct shapes. No one is quite sure why there are so many varieties of calcite, but impurities, temperature and composition during growth all may create variations on basic shapes. There are three basic shapes: trigonal prism, scalenohedron, and rhombohedron. The crystals shown here are scalenohedron.

Calcite

Calcite

Calcite crystalline stalactite "brush". Calcite has been found in over 2,500 distinct shapes. No one is quite sure why there are so many varieties of calcite, but impurities, temperature and composition during growth all may create variations on basic shapes. There are three basic shapes: trigonal prism, scalenohedron, and rhombohedron.

Calcite

Calcite has been found in over 2,500 distinct shapes. No one is quite sure why there are so many varieties of calcite, but impurities, temperature and composition during growth all may create variations on basic shapes. There are three basic shapes: trigonal prism, scalenohedron, and rhombohedron.

Calcite

Calcite has been found in over 2,500 distinct shapes. No one is quite sure why there are so many varieties of calcite, but impurities, temperature and composition during growth all may create variations on basic shapes. There are three basic shapes: trigonal prism, scalenohedron, and rhombohedron.

Calcite

Pure calcite, which has a chemical composition of CaCO3, is white. The pink color of this specimen is caused by impurities of manganese.

Calcite (on Quartz)

This specimen grew in two stages. First, amethyst crystals formed in an underground cavity from water containing dissolved silica. Later, another solution entered the cavity and formed the calcite crystals on top.

Calcite Spires

Calcite has been found in over 2,500 distinct shapes. No one is quite sure why there are so many varieties of calcite, but impurities, temperature and composition during growth all may create variations on basic shapes. There are three basic shapes: trigonal prism, scalenohedron, and rhombohedron.

Calcite Stalagmites

These small stalactites are composed of tiny calcite crystals that grew as water containing dissolved minerals dripped from the roof of a cave.

Calcite with goethite

Millions of microscopic calcite crystals make up these stalactites, colored red by goethite. As they grew in a small cavity in limestone, a change in conditions resulted in a second generation of large, blocky calcite crystals.

Calcite with sphalerite and fluorite

The football-shaped mineral is calcite - here two large, twinned crystals. The black crystals are sphalerite, a source of zinc; the purple crystals are fluorite. Rarely do large crystals, such as these, survive the mining process.

Malachite

The minerals azurite and malachite are commonly found together -- even in the same specimen. Both minerals consist of copper, carbonate, and water -- but in different arangements and proportions.

Malachite

The minerals azurite and malachite are commonly found together -- even in the same specimen. Both minerals consist of copper, carbonate, and water -- but in different arangements and proportions.

Malachite

Often used as an ornamental stone in jewelry, amulets, powder for eye makeup and pigment for paint, Malachite grows in layers of tiny crystals. Its colors correlate with different crystal sizes: small crystals form light green bands and larger crystals make darker ones.

Malachite (polished slab)

Often used as an ornamental stone in jewelry, amulets, powder for eye makeup and pigment for paint, Malachite grows in layers of tiny crystals. Its colors correlate with different crystal sizes: small crystals form light green bands and larger crystals make darker ones.

Rhodochrosite

One of the minerals used for the 1974 Mineral Heritage Stamps, rhodochrosite is also known as manganesespar and raspberryspar. Its name is derived from the greek rhodon, meaning "rose" and chroma, meaning "color", referring to its rosy color. It is a manganese carbonate mineral and is a relatively soft stone, ranking only 3.5 to 4 on the Moh's Scale of Hardness. It also has three directions of cleavage (the quality of a crystallized substance or rock of splitting along definite planes), which does not make it a very durable stone to use for commonly-worn jewelry like rings. Rhodochrosite is commonly found associated with calcite, quartz and metal sulfides. Each reddish-pink crystal is shaped like a distorted cube, or rhombohedron. This specimen was collected from a gold and silver mine in Silverton, CO.

Rhodochrosite

One of the minerals used for the 1974 Mineral Heritage Stamps, rhodochrosite is also known as manganesespar and raspberryspar. Its name is derived from the greek rhodon, meaning "rose" and chroma, meaning "color", referring to its rosy color. It is a manganese carbonate mineral and is a relatively soft stone, ranking only 3.5 to 4 on the Moh's Scale of Hardness. It also has three directions of cleavage (the quality of a crystallized substance or rock of splitting along definite planes), which does not make it a very durable stone to use for commonly-worn jewelry like rings. Rhodochrosite is commonly found associated with calcite, quartz and metal sulfides.

Rhodochrosite

One of the minerals used for the 1974 Mineral Heritage Stamps, rhodochrosite is also known as manganesespar and raspberryspar. Its name is derived from the greek rhodon, meaning "rose" and chroma, meaning "color", referring to its rosy color. It is a manganese carbonate mineral and is a relatively soft stone, ranking only 3.5 to 4 on the Moh's Scale of Hardness. It also has three directions of cleavage (the quality of a crystallized substance or rock of splitting along definite planes), which does not make it a very durable stone to use for commonly-worn jewelry like rings. Rhodochrosite is commonly found associated with calcite, quartz and metal sulfides. Manganese colors rhodochrosite red; crystals of this intensity and quality are very rare.

Rhodochrosite with Quartz

One of the minerals used for the 1974 Mineral Heritage Stamps, rhodochrosite is also known as manganesespar and raspberryspar. Its name is derived from the greek rhodon, meaning "rose" and chroma, meaning "color", referring to its rosy color. It is a manganese carbonate mineral and is a relatively soft stone, ranking only 3.5 to 4 on the Moh's Scale of Hardness. It also has three directions of cleavage (the quality of a crystallized substance or rock of splitting along definite planes), which does not make it a very durable stone to use for commonly-worn jewelry like rings. Rhodochrosite is commonly found associated with calcite, quartz and metal sulfides, and is always pink or red because it contains manganese. This extraordinary specimen was found during mining for tungsten.

Siderite

Quartz crystal fans on Siderite.

Smithsonite

The mineral smithsonite was named after James Smithson, the British chemist and mineralogist who first recognized it as a distinct mineral, different from calamine(hemimorphite). It is mined for zinc. James Smithson (1754-1829) was the founder of the Smithsonian Institution.