The Flickr Pseudohexagonal Image Generatr

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The carbonate minerals all contain one or more carbonate (CO3-2) anions.

Aragonite has the same chemistry as calcite - it is calcium carbonate (CaCO3). Why is it a different mineral? Aragonite has a different molecular structure - the atoms are packed differently. Different minerals having the same chemical formula are called polymorphs (another good example is graphite & diamond - both C).

The difference in atomic-level packing between calcite and aragonite can be seen at the level of mineral hand samples. Aragonite forms crystals in the orthorhombic class. Many aragonite crystals are acicular (needle-like). Many aragonites form pseudohexagonal crystals, the result of 6 orthorhombic prisms growing parallel to each other. The specimen seen here is a side view of a cyclic-twinned, pseudohexagonal aragonite mass.

Aragonite is slightly harder than calcite, at H=3.5 to 4, occurs in many colors, and easily bubbles in acid. Aragonite is a little bit heavier than calcite, due to closer packing of atoms.

Most modern seashells & coral skeletons are composed of the aragonite. Whitish-colored lime sand beaches in the world are aragonitic. Occasionally, "whitings" are seen in shallow, warm ocean environments. Whitings (cloudy, milky seawater) turn out to be loaded with tiny hair-like needles of aragonite.

In the rock record, aragonitic or aragonite-rich sediments convert to calcite over time. Cenozoic-aged carbonate sedimentary rocks are often aragonitic. Mesozoic- and Paleozoic-aged carbonates are almost always calcitic. Many ancient fossils have had their aragonitic shells dissolved away. Ancient shells that were originally calcitic are often still well preserved.

Locality: unrecorded / undisclosed, but possibly from Spain
-----------------
Photo gallery of aragonite:
www.mindat.org/gallery.php?min=307

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The carbonate minerals all contain one or more carbonate (CO3-2) anions.

Aragonite has the same chemistry as calcite - it is calcium carbonate (CaCO3). Why is it a different mineral? Aragonite has a different molecular structure - the atoms are packed differently. Different minerals having the same chemical formula are called polymorphs (another good example is graphite & diamond - both C).

The difference in atomic-level packing between calcite and aragonite can be seen at the level of mineral hand samples. Aragonite forms crystals in the orthorhombic class. Many aragonite crystals are acicular (needle-like). Many aragonites form pseudohexagonal crystals, the result of 6 orthorhombic prisms growing parallel to each other. The specimen seen here is a side view of a cyclic-twinned, pseudohexagonal aragonite mass.

Aragonite is slightly harder than calcite, at H=3.5 to 4, occurs in many colors, and easily bubbles in acid. Aragonite is a little bit heavier than calcite, due to closer packing of atoms.

Most modern seashells & coral skeletons are composed of the aragonite. Whitish-colored lime sand beaches in the world are aragonitic. Occasionally, "whitings" are seen in shallow, warm ocean environments. Whitings (cloudy, milky seawater) turn out to be loaded with tiny hair-like needles of aragonite.

In the rock record, aragonitic or aragonite-rich sediments convert to calcite over time. Cenozoic-aged carbonate sedimentary rocks are often aragonitic. Mesozoic- and Paleozoic-aged carbonates are almost always calcitic. Many ancient fossils have had their aragonitic shells dissolved away. Ancient shells that were originally calcitic are often still well preserved.

Locality: unrecorded / undisclosed, but possibly from Spain
-----------------
Photo gallery of aragonite:
www.mindat.org/gallery.php?min=307

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The carbonate minerals all contain one or more carbonate (CO3-2) anions.

Aragonite has the same chemistry as calcite - it is calcium carbonate (CaCO3). Why is it a different mineral? Aragonite has a different molecular structure - the atoms are packed differently. Different minerals having the same chemical formula are called polymorphs (another good example is graphite & diamond - both C).

The difference in atomic-level packing between calcite and aragonite can be seen at the level of mineral hand samples. Aragonite forms crystals in the orthorhombic class. Many aragonite crystals are acicular (needle-like). Many aragonites form pseudohexagonal crystals, the result of 6 orthorhombic prisms growing parallel to each other. The specimen seen here is a side view of a cyclic-twinned, pseudohexagonal aragonite mass.

Aragonite is slightly harder than calcite, at H=3.5 to 4, occurs in many colors, and easily bubbles in acid. Aragonite is a little bit heavier than calcite, due to closer packing of atoms.

Most modern seashells & coral skeletons are composed of the aragonite. Whitish-colored lime sand beaches in the world are aragonitic. Occasionally, "whitings" are seen in shallow, warm ocean environments. Whitings (cloudy, milky seawater) turn out to be loaded with tiny hair-like needles of aragonite.

In the rock record, aragonitic or aragonite-rich sediments convert to calcite over time. Cenozoic-aged carbonate sedimentary rocks are often aragonitic. Mesozoic- and Paleozoic-aged carbonates are almost always calcitic. Many ancient fossils have had their aragonitic shells dissolved away. Ancient shells that were originally calcitic are often still well preserved.

Locality: unrecorded / undisclosed, but possibly from Spain
-----------------
Photo gallery of aragonite:
www.mindat.org/gallery.php?min=307

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The carbonate minerals all contain one or more carbonate (CO3-2) anions.

Aragonite has the same chemistry as calcite - it is calcium carbonate (CaCO3). Why is it a different mineral? Aragonite has a different molecular structure - the atoms are packed differently. Different minerals having the same chemical formula are called polymorphs (another good example is graphite & diamond - both C).

The difference in atomic-level packing between calcite and aragonite can be seen at the level of mineral hand samples. Aragonite forms crystals in the orthorhombic class. Many aragonite crystals are acicular (needle-like). Many aragonites form pseudohexagonal crystals, the result of 6 orthorhombic prisms growing parallel to each other. The specimen seen here is a side view of a cyclic-twinned, pseudohexagonal aragonite mass.

Aragonite is slightly harder than calcite, at H=3.5 to 4, occurs in many colors, and easily bubbles in acid. Aragonite is a little bit heavier than calcite, due to closer packing of atoms.

Most modern seashells & coral skeletons are composed of the aragonite. Whitish-colored lime sand beaches in the world are aragonitic. Occasionally, "whitings" are seen in shallow, warm ocean environments. Whitings (cloudy, milky seawater) turn out to be loaded with tiny hair-like needles of aragonite.

In the rock record, aragonitic or aragonite-rich sediments convert to calcite over time. Cenozoic-aged carbonate sedimentary rocks are often aragonitic. Mesozoic- and Paleozoic-aged carbonates are almost always calcitic. Many ancient fossils have had their aragonitic shells dissolved away. Ancient shells that were originally calcitic are often still well preserved.

Locality: unrecorded / undisclosed, but possibly from Spain
-----------------
Photo gallery of aragonite:
www.mindat.org/gallery.php?min=307

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The carbonate minerals all contain one or more carbonate (CO3-2) anions.

Aragonite has the same chemistry as calcite - it is calcium carbonate (CaCO3). Why is it a different mineral? Aragonite has a different molecular structure - the atoms are packed differently. Different minerals having the same chemical formula are called polymorphs (another good example is graphite & diamond - both C).

The difference in atomic-level packing between calcite and aragonite can be seen at the level of mineral hand samples. Aragonite forms crystals in the orthorhombic class. Many aragonite crystals are acicular (needle-like). Many aragonites form pseudohexagonal crystals, the result of 6 orthorhombic prisms growing parallel to each other. The specimen seen here is a top view of a cyclic-twinned, pseudohexagonal aragonite mass.

Aragonite is slightly harder than calcite, at H=3.5 to 4, occurs in many colors, and easily bubbles in acid. Aragonite is a little bit heavier than calcite, due to closer packing of atoms.

Most modern seashells & coral skeletons are composed of the aragonite. Whitish-colored lime sand beaches in the world are aragonitic. Occasionally, "whitings" are seen in shallow, warm ocean environments. Whitings (cloudy, milky seawater) turn out to be loaded with tiny hair-like needles of aragonite.

In the rock record, aragonitic or aragonite-rich sediments convert to calcite over time. Cenozoic-aged carbonate sedimentary rocks are often aragonitic. Mesozoic- and Paleozoic-aged carbonates are almost always calcitic. Many ancient fossils have had their aragonitic shells dissolved away. Ancient shells that were originally calcitic are often still well preserved.

Locality: unrecorded / undisclosed, but possibly from Spain
-----------------
Photo gallery of aragonite:
www.mindat.org/gallery.php?min=307

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The carbonate minerals all contain one or more carbonate (CO3-2) anions.

Aragonite has the same chemistry as calcite - it is calcium carbonate (CaCO3). Why is it a different mineral? Aragonite has a different molecular structure - the atoms are packed differently. Different minerals having the same chemical formula are called polymorphs (another good example is graphite & diamond - both C).

The difference in atomic-level packing between calcite and aragonite can be seen at the level of mineral hand samples. Aragonite forms crystals in the orthorhombic class. Many aragonite crystals are acicular (needle-like). Many aragonites form pseudohexagonal crystals, the result of 6 orthorhombic prisms growing parallel to each other. The specimen seen here is a top view of a cyclic-twinned, pseudohexagonal aragonite mass.

Aragonite is slightly harder than calcite, at H=3.5 to 4, occurs in many colors, and easily bubbles in acid. Aragonite is a little bit heavier than calcite, due to closer packing of atoms.

Most modern seashells & coral skeletons are composed of the aragonite. Whitish-colored lime sand beaches in the world are aragonitic. Occasionally, "whitings" are seen in shallow, warm ocean environments. Whitings (cloudy, milky seawater) turn out to be loaded with tiny hair-like needles of aragonite.

In the rock record, aragonitic or aragonite-rich sediments convert to calcite over time. Cenozoic-aged carbonate sedimentary rocks are often aragonitic. Mesozoic- and Paleozoic-aged carbonates are almost always calcitic. Many ancient fossils have had their aragonitic shells dissolved away. Ancient shells that were originally calcitic are often still well preserved.

Locality: unrecorded / undisclosed, but possibly from Spain
-----------------
Photo gallery of aragonite:
www.mindat.org/gallery.php?min=307

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The carbonate minerals all contain one or more carbonate (CO3-2) anions.

Aragonite has the same chemistry as calcite - it is calcium carbonate (CaCO3). Why is it a different mineral? Aragonite has a different molecular structure - the atoms are packed differently. Different minerals having the same chemical formula are called polymorphs (another good example is graphite & diamond - both C).

The difference in atomic-level packing between calcite and aragonite can be seen at the level of mineral hand samples. Aragonite forms crystals in the orthorhombic class. Many aragonite crystals are acicular (needle-like). Many aragonites form pseudohexagonal crystals, the result of 6 orthorhombic prisms growing parallel to each other. The specimen seen here is a side view of a cyclic-twinned, pseudohexagonal aragonite mass.

Aragonite is slightly harder than calcite, at H=3.5 to 4, occurs in many colors, and easily bubbles in acid. Aragonite is a little bit heavier than calcite, due to closer packing of atoms.

Most modern seashells & coral skeletons are composed of the aragonite. Whitish-colored lime sand beaches in the world are aragonitic. Occasionally, "whitings" are seen in shallow, warm ocean environments. Whitings (cloudy, milky seawater) turn out to be loaded with tiny hair-like needles of aragonite.

In the rock record, aragonitic or aragonite-rich sediments convert to calcite over time. Cenozoic-aged carbonate sedimentary rocks are often aragonitic. Mesozoic- and Paleozoic-aged carbonates are almost always calcitic. Many ancient fossils have had their aragonitic shells dissolved away. Ancient shells that were originally calcitic are often still well preserved.

Locality: unrecorded / undisclosed, but possibly from Spain
-----------------
Photo gallery of aragonite:
www.mindat.org/gallery.php?min=307

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The carbonate minerals all contain one or more carbonate (CO3-2) anions.

Aragonite has the same chemistry as calcite - it is calcium carbonate (CaCO3). Why is it a different mineral? Aragonite has a different molecular structure - the atoms are packed differently. Different minerals having the same chemical formula are called polymorphs (another good example is graphite & diamond - both C).

The difference in atomic-level packing between calcite and aragonite can be seen at the level of mineral hand samples. Aragonite forms crystals in the orthorhombic class. Many aragonite crystals are acicular (needle-like). Many aragonites form pseudohexagonal crystals, the result of 6 orthorhombic prisms growing parallel to each other. The specimen seen here is a top view of a cyclic-twinned, pseudohexagonal aragonite mass.

Aragonite is slightly harder than calcite, at H=3.5 to 4, occurs in many colors, and easily bubbles in acid. Aragonite is a little bit heavier than calcite, due to closer packing of atoms.

Most modern seashells & coral skeletons are composed of the aragonite. Whitish-colored lime sand beaches in the world are aragonitic. Occasionally, "whitings" are seen in shallow, warm ocean environments. Whitings (cloudy, milky seawater) turn out to be loaded with tiny hair-like needles of aragonite.

In the rock record, aragonitic or aragonite-rich sediments convert to calcite over time. Cenozoic-aged carbonate sedimentary rocks are often aragonitic. Mesozoic- and Paleozoic-aged carbonates are almost always calcitic. Many ancient fossils have had their aragonitic shells dissolved away. Ancient shells that were originally calcitic are often still well preserved.

Locality: unrecorded / undisclosed, but possibly from Spain
-----------------
Photo gallery of aragonite:
www.mindat.org/gallery.php?min=307

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The carbonate minerals all contain one or more carbonate (CO3-2) anions.

Aragonite has the same chemistry as calcite - it is calcium carbonate (CaCO3). Why is it a different mineral? Aragonite has a different molecular structure - the atoms are packed differently. Different minerals having the same chemical formula are called polymorphs (another good example is graphite & diamond - both C).

The difference in atomic-level packing between calcite and aragonite can be seen at the level of mineral hand samples. Aragonite forms crystals in the orthorhombic class. Many aragonite crystals are acicular (needle-like). Many aragonites form pseudohexagonal crystals, the result of 6 orthorhombic prisms growing parallel to each other. The specimen seen here is a top view of a cyclic-twinned, pseudohexagonal aragonite mass.

Aragonite is slightly harder than calcite, at H=3.5 to 4, occurs in many colors, and easily bubbles in acid. Aragonite is a little bit heavier than calcite, due to closer packing of atoms.

Most modern seashells & coral skeletons are composed of the aragonite. Whitish-colored lime sand beaches in the world are aragonitic. Occasionally, "whitings" are seen in shallow, warm ocean environments. Whitings (cloudy, milky seawater) turn out to be loaded with tiny hair-like needles of aragonite.

In the rock record, aragonitic or aragonite-rich sediments convert to calcite over time. Cenozoic-aged carbonate sedimentary rocks are often aragonitic. Mesozoic- and Paleozoic-aged carbonates are almost always calcitic. Many ancient fossils have had their aragonitic shells dissolved away. Ancient shells that were originally calcitic are often still well preserved.

Locality: unrecorded / undisclosed, but possibly from Spain
-----------------
Photo gallery of aragonite:
www.mindat.org/gallery.php?min=307

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The carbonate minerals all contain one or more carbonate (CO3-2) anions.

Aragonite has the same chemistry as calcite - it is calcium carbonate (CaCO3). Why is it a different mineral? Aragonite has a different molecular structure - the atoms are packed differently. Different minerals having the same chemical formula are called polymorphs (another good example is graphite & diamond - both C).

The difference in atomic-level packing between calcite and aragonite can be seen at the level of mineral hand samples. Aragonite forms crystals in the orthorhombic class. Many aragonite crystals are acicular (needle-like). Many aragonites form pseudohexagonal crystals, the result of 6 orthorhombic prisms growing parallel to each other. The specimen seen here is a top view of a cyclic-twinned, pseudohexagonal aragonite mass.

Aragonite is slightly harder than calcite, at H=3.5 to 4, occurs in many colors, and easily bubbles in acid. Aragonite is a little bit heavier than calcite, due to closer packing of atoms.

Most modern seashells & coral skeletons are composed of the aragonite. Whitish-colored lime sand beaches in the world are aragonitic. Occasionally, "whitings" are seen in shallow, warm ocean environments. Whitings (cloudy, milky seawater) turn out to be loaded with tiny hair-like needles of aragonite.

In the rock record, aragonitic or aragonite-rich sediments convert to calcite over time. Cenozoic-aged carbonate sedimentary rocks are often aragonitic. Mesozoic- and Paleozoic-aged carbonates are almost always calcitic. Many ancient fossils have had their aragonitic shells dissolved away. Ancient shells that were originally calcitic are often still well preserved.

Locality: unrecorded / undisclosed, but possibly from Spain
-----------------
Photo gallery of aragonite:
www.mindat.org/gallery.php?min=307

Aragonite (detail). The mineral is calcium carbonate. These are a pseudohexagonal form of orthorhombic twins. Tazouta Mine. Sefrou Cercle, Sefrou Province, Fès-Meknès Region, Morocco.

Aragonite. The mineral is calcium carbonate. These are a pseudohexagonal form of orthorhombic twins. Tazouta Mine. Sefrou Cercle, Sefrou Province, Fès-Meknès Region, Morocco.

Hendricksite. The mineral, a rare member of the mica group, is hydrous potassium zinc aluminum silicate. It is the only zinc-bearing mica. This specimen is from a co-type locality. Franklin Mine. Franklin Mining District. Franklin, Sussex Co., New Jersey.

Locality: La Pesquera, Cuenca, Castile-La Mancha, Spain
Size: Crystal is 2.8 inches tall.

Locality: Morocco
Size: Central crystal is 1.60 inches tall.

Locality:
Size: Crystal is 1.69 inches wide and 1.34 inches tall.

This is one of the two mineral forms of calcium carbonate; the other is calcite. Aragonite forms at lower temperatures and/or higher pressures than calcite. It is considered unstable and can convert to calcite. This twinned cluster shows pseudo-hexagonal form.

Aragonite can also have biogenic origins (ie mollusk shells).

I purchased this twinned specimen at the Sac. Mineral Society's November show.

One and a half inches of pure crystalline magic...