Micro Quartz Mineral Basics

Chalcedony, Agate & Jasper Are Popular Varieties

The core of this thunder egg from Nevada is composed of microcrystalline quartz. Richard Gross

Quartz minerals are usually thought of as large single crystals. Microcrystalline quartz, however, is dense with crystal grains so small that an optical microscope is necessary to view the individual crystals. When those crystals are so small they cannot individually be seen using a specialized microscope, they are called cryptocrystalline.


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The general term, chalcedony, refers to varieties of quartz where microcrystalline and cryptocrystalline crystals intertwine and grow together. There are many varieties of chalcedony in different colors and patterns. They are plentiful and popular. Gem-grade chalcedony is generally light blue, white or gray and often called holly blue. Chalcedony’s name is said to come from the Greek port of Chalcedon.

Varieties of Microcrystalline Quartz

Agate – Curved banded variety

Jasper – Opaque, red or green varieties

Chert – General name used for compact, hard rocks that contain microcrystalline quartz

Flint – Afiner-grained, harder type of chert, Ohio’s official gemstone

Chrysoprase is a type of microcrystalline quartz prized for use in the jewelry trade. Photo by Richard Gross

Carnelian – Orange-red opaque mineral

Onyx – Parallel banded variety

Sardonyx – Red sard and white chalcedony

Chrysoprase – Translucent, apple-green color

Bloodstone – Dark green with red spots of iron oxide

Petrified Wood – Over time chalcedony replaces wood while preserving the growth rings

Happy Micro Quartz

Microcrystalline quartz has so many beautiful varieties that it’s often interwoven into our pop culture. It’s a happy birthday for these micro quartz birthstones – bloodstone (May) and sardonyx (August). Chalcedony itself is said to bring stability and balance to its bearer.

This story about micro quartz minerals previously appeared in Rock & Gem magazine. Click here to subscribe. Story by Richard Gross and Pam Freeman.


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