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Jasper

earth science Maturity 11-13 Next article →

Jasper is a colorful and opaque rock made of silica. It is an aggregate, which means it is a collection of tiny grains. These grains are usually microgranular quartz or cryptocrystalline chalcedony. Unlike gemstones that you can see through, jasper is opaque. This means light does not pass through it easily. It comes in many colors like red, yellow, brown, or green. Blue jasper is also very rare. The most common color is red. This happens because of iron(III) inclusions, which are tiny bits of iron trapped inside the stone.

Red jasper amulet HARGM7392
Red jasper amulet HARGM7392

How does jasper form in nature? The process often begins with silica-rich sediment or volcanic ash. Scientists believe that hydrothermal circulation is required for this to happen. This means hot water moves through the earth and carries minerals. As these materials settle and consolidate, they form different patterns. Some patterns come from how the ash or sediment was originally laid down. Other patterns happen when minerals move through cracks. This movement can create dendritic patterns, which look like growing plants. Over time, weathering can also create colorful outer layers called rinds.

Jasper earrings
Jasper earrings

Jasper can appear in many different types and patterns. Some stones are called "picture jaspers" because they look like they have scenes inside them. These patterns come from many sources. For example, orbicular patterns look like leopard skin. This happens when minerals diffuse, or spread out, from a center point. You might also see linear banding, which looks like stripes. This is called liesegang jasper. Sometimes, the rock is broken and then filled with new minerals. This creates a look called brecciated jasper.

Jasper vase WB.71
Jasper vase WB.71

Humans have valued jasper for thousands of years. The name comes from the Greek word "iaspis," meaning spotted or speckled stone. Its history is tied to many ancient cultures. On Minoan Crete, people carved jasper seals around 1800 BC. In the Indus Valley, people carved red jasper into shapes like a male torso.

Harappa red jasper male torso
Harappa red jasper male torso

Ancient Hebrew texts might even describe jasper. The stone "odem" might have been red jasper. The stone "tarshish" may have been a yellow variety. In the Nibelungenlied, a famous poem, jasper is described as being green and clear.

Because jasper is very dense, it is a sturdy material. Its density is typically between 2.5 and 2.9 g/cm3. It breaks with a smooth surface and can be highly polished. This makes it perfect for ornamentation. People have used it to make beautiful objects like vases, seals, and snuff boxes.

Jasper goat basket (Russia, 19 c.)
Jasper goat basket (Russia, 19 c.)

You can find jasper in many places around the world. Indonesia is a known source, especially in the Purbalingga district. In the United States, you can find fine examples like Biggs jasper in Oregon. You can also find Bruneau jasper in the Bruneau River canyon in Idaho.

Egyptian - Finger Ring with a Representation of Ptah - Walters 42387 - Side A
Egyptian - Finger Ring with a Representation of Ptah - Walters 42387 - Side A

Jasper also tells us about the history of our planet. It is a main part of banded iron formations, or BIFs. These are rocks that contain distinct layers of jasper and iron. These formations are very important to scientists. They show us when there were small amounts of dissolved oxygen in the water. This happened during massive periods like the Great Oxidation Event or "Snowball Earth." The red bands in these rocks are actually microcrystalline red chert, which is another name for jasper.

Jasper earrings
Jasper earrings

Finally, jasper is related to other dark, dense stones. One such stone is basanite, a deep black variety of quartz. In ancient times, a similar black stone was called a touchstone. The ancient Greeks called it the Lydian stone after the kingdom of Lydia. People used these stones to test if precious metals were pure. They would scrape the metal across the hard stone. The metal would leave a colored streak on the dark background. This helped them see the true color of the metal alloy.

Necklace And Pendant (possibly France), ca. 1870 (CH 18423329)
Necklace And Pendant (possibly France), ca. 1870 (CH 18423329)
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🖼️ Images & Media (7)
File:Egyptian - Finger Ring with a Representation of Ptah - Walters 42387 - Side A.jpg
Egyptian - Finger Ring with a...
File:Red jasper amulet HARGM7392.JPG
Red jasper amulet HARGM7392.JPG
File:Necklace And Pendant (possibly France), ca. 1870 (CH 18423329).jpg
Necklace And Pendant (possibly France),...
File:Harappa red jasper male torso.jpg
Harappa red jasper male torso.jpg
File:Jasper vase WB.71.jpg
Jasper vase WB.71.jpg
File:Jasper goat basket (Russia, 19 c.).jpg
Jasper goat basket (Russia, 19 c.).jpg
File:Jasper earrings.jpg
Jasper earrings.jpg
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