Nature's Inorganic Creations

Houston Museum of Natural Science

A selection of items from the Cullen Hall of Gems and Minerals

From a huge blue topaz crystal weighing more than 2,000 carats to a crystallized gold cluster that is one of the most highly coveted objects in the mineral kingdom, the spectacular specimens on display here are true masterpieces – the Rembrandts and Picassos of the natural world.

This piece was collected from a mine in Mexico. Amazingly, the gypsum formed over a piece of rope and some metalwork. The mine had been abandoned for decades, and in the absence of human activity, geologic forces took over. Gypsum crystals grow faster than some other minerals, like quartz. Quartz crystals this size would have taken hundreds, or even thousands of years to grow, depending on the conditions. In another part of Mexico, there is a cave with gypsum crystals 30 feet long and several feet across.

Pyrite is also known as “fool’s gold” because of its golden, metallic appearance. In reality, pyrite is iron sulfide, and is not nearly as valuable as gold. Its name means “fire rock” and comes from the fact that striking iron against this mineral can create sparks. In Central America, the ancient Maya made mirrors from this mineral by grinding fine stones against its surface, like sandpaper, until it was polished to a mirror finish.

Wulfenite has been called the supermodel of the mineral world. Many of the other minerals in our hall have a variety of uses in the jewelry industry and in manufacturing, but wulfenite does not; it just looks pretty. It is popular with collectors, who prize the mineral for its flower-like appearance and its unusual, orange color.

This geode started life as a bubble in a lava flow, long ago. Gases trapped in this bubble condensed to form amethyst quartz crystals. It took thousands of years for these crystals to form. The unique purple color of amethyst quartz comes from impurities of iron within the crystal structure.

Fluorite can often be found in cubes, like this one, or in octahedrons or double pyramids. In fact, you can see an inverted pyramid inside this specimen, revealing the crystalline structure than can be either cubes or octahedrons. Fluoride comes from fluorite, and is used in drinking water and toothpaste to promote dental health.

Rhodochrosite is a beautiful mineral, but it is not often used in jewelry because of how soft it is. On the Mohs hardness scale, it rates a 3.5 – 4, a little harder than your fingernail.

This rhodochrosite originally formed as a stalactite in a cave, which is why you can see growth rings in this cross-section. The stalactite was sliced and polished, resulting in this delicious looking specimen.

One of the most abundant minerals on Earth is quartz. Quartz is valued for its beauty, when it is free of impurities, but it also has many industrial uses in electronics, optics, and filters.

Stibnite is very soft, only a 2 on the Mohs hardness scale, slightly softer than your fingernail. You wouldn’t want to touch stibnite, though, as it is antimony sulfide and is a poisonous material. Stibnite is primarily used for industrial purposes, such as metal smelting and matches. Because of its softness, when a rather large piece was brought to the museum it was put into a crate, and then the crate was filled with powder detergent to hold the delicate crystals in place. Its metallic luster is unusual and attracts collectors. Specimens of this size are rarely found.

This type of specimen is formed in kaolinite clay and crystals are compressed laterally to make the “sun” or “star” shape. Found in Australia, the Malbunka Mine is the only mine in the world that currently produces the disk shape blue suns.

This vase is made of malachite. Malachite was used by the ancient Egyptians to produce green and blue pigments and jewelry, and also to produce green cosmetics, like eyeliner. Its chemical formula is very similar to that of azurite, and the two minerals can often be found together.

Mesolite in large crystals and large, spherical sprays like the one pictured here come from only one place in the world: the Pashan Hills quarries.

The 23-cm example shown here, on fluorapophyllite matrix, is probably the world’s finest example of the species.

This specimen is extremely fragile and was brought out of India by mineral dealer Rock Currier, who packed the specimen in powdered soap and bought for it a first-class airplane ticket from Bombay to Los Angeles in order to ensure its safe arrival.

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The story featured may in some cases have been created by an independent third party and may not always represent the views of the institutions, listed below, who have supplied the content.
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