Agate Value, Price, and Jewelry Information

What you'll learn in this article:

• The scientific definition and composition of agate stones
• The stunning varieties of agates from around the world
• How agates form and how they're enhanced
• What factors determine their value
• Where different varieties come from
• How agates are used in jewelry

What is Agate?

Agate is a remarkable variety of chalcedony, a cryptocrystalline form of quartz that occurs naturally in an incredible range of colors and patterns. Its patterns, translucency, and sometimes moss-like inclusions can distinguish agates from other chalcedonies. 

Some notable facts about agate stone include:

• Agates can be opaque, translucent, or occasionally completely transparent.
• Agate's vivid colors result from traces of iron, manganese, titanium, chromium, and nickel oxides as well as other elements.
• These stones are renowned for taking an exceptional polish.
• They have remarkable durability, which makes them tough enough for most jewelry applications.
• Designers often take advantage of agate's intriguing patterns to create unique and fascinating jewelry pieces.

Exploring Varieties of Agate Stones

Gemologists usually describe agate varieties by their color patterns, inclusions, or sources. The color patterns in agates usually take the form of flat or concentric layers or bands. Mossy or dendritic ("tree-like") inclusions can sometimes create the impression of vegetation and landscapes.

Banded Agate

Banded agates feature regular color layers and bright colors, making them incredibly popular. However, keep in mind that many of the richly colored banded agates you find for sale are dyed commercially. Although banded agates occur all over the world, Brazil stands out as one of the most productive sources.

Moss, Plume, and Dendritic Agate

These unique varieties contain intriguing mineral oxide inclusions that can show any color. The appearance of these inclusions determines the variety as follows:

• Moss agates have plant-like patterns.
• Plume agates showcase feather-like formations.
• Dendritic agates display tree-like, branching patterns.

Picture or Scenic Agate

Some remarkable agates have inclusions that can create the appearance of entire landscapes within them, complete with lakes, shorelines, trees, and shrubs. Collectors particularly treasure these "natural picture" stones.

Fire Agate

Due to inclusions of plate-like crystals of iron hydroxides called limonite, fire agates exhibit stunning iridescence. Careful cutting and polishing can enhance this effect.

Lace Agate

Characterized by delicate designs, lace agates show bands with intricate swirls and loops. Mexico is one of the premier sources of this material.

Other Agate Varieties

• Iris agates show iridescent colors between color layers.
• Shell agates feature patterns created by embedded, silicified shells.
• Turritella agates consist primarily of shells and shell fragments of the gastropod genus Turritella and certain other species.

Petrified Wood Agate

Fossilized ancient tree trunks and limbs may have their organic components replaced by agate stone over millions of years. In some cases, their woody structure may also be preserved and visible with a microscope. The agate's color may be very bright and strong.

Agate Value: Factors Influencing Price and Desirability

The value of agates is generally quite modest. Three main factors determine the prices of these stones:

• Labor and artistry play a more significant role in pricing than the raw material's inherent value.
• Larger agates with distinctive, fine, or landscape-like color patterns command premium prices.
• Custom-cut pieces or stones from prized locations are substantially more expensive.

For more information on agate value, consult our comprehensive guides to buying agates and moss agate engagement rings.

Synthetics and Enhancements

For information on synthetic or lab-made quartz in general, consult our quartz gem listing.

An ancient enhancement technique for agates, dyeing remains a common practice. (Chalcedony stones are relatively porous, which makes dyeing these pieces easy). Dyeing is usually a stable process for agates.

A celebrated and secret process for dyeing agates originated in Idar-Oberstein, Germany, during the 19th century. When the local deposits were depleted, emigrants to South America shipped gray agates back to Idar-Oberstein. The resulting dyed agates proved extraordinary.

Enhancements should be disclosed to consumers to ensure marketplace transparency.

Global Sources of Agate Stones

Agate stones come from many locations worldwide:

• Moss agates: India, Scotland, northwestern United States.
• Scenic agates: Yellowstone National Park, Wyoming, Montana.
• Banded agates: Brazil, Uruguay, Madagascar, Mexico, United States.
• Lace agate: Mexico, Arizona, Namibia.
• Fire agates: Mexico.
• Petrified wood: Arizona, New Mexico, California, various European countries, and many other localties.

Stone Sizes and Formation

Agates typically form as nodules but can occasionally develop into masses weighing several pounds and spanning many inches in diameter.

Frequently Asked Questions

What exactly is an agate stone?

Geologists define it as a variety of chalcedony, a cryptocrystalline form of quartz. Agates can show many distinctive colors, patterns, inclusions, and degrees of translucence. Traces of iron, manganese, titanium, and chromium oxides create the stone's coloration.

How are agates typically valued?

Collectors and jewelers value agates modestly, focusing more on the skill and artistic work that goes into the finished jewelry than the raw material's inherent worth. Larger agates that showcase distinctive, fine, or landscape-like color patterns fetch higher prices. Custom-cut stones or those from prized locations typically command premium prices.

What are the most common varieties of agate?

Gem enthusiasts appreciate several popular varieties, such as:

• Banded agates with regular color layers
• Moss agates with plant-like patterns
• Plume agates featuring feather-like formations
• Dendritic agates with tree-like branching patterns
• Picture or scenic agates showing landscape-like inclusions
• Fire agates with iridescent limonite crystals
• Lace agates with intricate swirls and loops

Where are agates typically found?

Gem hunters discover agate stones in many locations around the world. Brazil is one of the productive sources of banded agates. Mexico is an important source of lace agates.

What are the most common enhancements for agates showcased in jewelry and mineral collections?

Artisans have long used dyeing as a primary enhancement technique for agates. Chalcedony stones' porous structure allows them to absorb dyes easily.

Can agates form in large sizes?

Typically, gem hunters find agates as small nodules. However, these stones can occasionally grow into massive formations weighing several pounds.

Are all agates naturally colored?

Many agates undergo commercial dyeing processes. Banded agates, in particular, often feature artificially enhanced colors. Ethical gem dealers always disclose these enhancements to consumers, ensuring transparency in the marketplace.