Agate is part of a group of minerals called chalcedony, a subtype of quartz. The most common chalcedony on the planet, it is technically classed as a silica mineraloid.Some of agate’s relatives in the chalcedony category include carnelian, onyx, and jasper.
Is agate a gem or a stone?
Both! It’s a gemstone. As a member of the quartz group, it rates a 7 to 7.5 on the Mohs Hardness Scale, just below topaz.
How is agate formed?
What sets agate apart from many other chalcedonies is its characteristic banding. This is built as silica-rich water repeatedly flows up into the cavities and voids of other rocks. Each new deposit helps to establish a new layer. This process is completed over millions of years, so you can consider your agate a real labor of love from planet Earth.Agate forms all over the world, but some of the most common places it’s found include Brazil, Germany, Mexico, Russia, Morocco, India, Thailand, China, Mongolia, Uruguay, and the western United States.
Is agate microcrystalline or cryptocrystalline?
Many gemologists will describe agate as either microcrystalline or cryptocrystalline. Microcrystalline stones are composed of tiny crystals that can be picked up visually under strong magnification. The crystals that make up a cryptocrystalline piece cannot.In truth, agate can be either. It depends on the variety of agate and the strength of the microscope. Either way, its true composition cannot be observed by the naked eye.
Agate or geode? Is there a difference?
Geodes are hollow rocks with crystal formations inside, whereas agate is typically a solid formation.If you’ve ever gone hunting for your own geodes, you know they’re frequently their own, potato-shaped rock, just waiting to be cracked open for the big reveal. Agate, on the other hand, builds up in the nodules and seams of other rocks.
That said, you never know – you could crack open a geode to find agate inside! It’s relatively normal to find some layers of agate among a geode’s crystals.
What about coral agate?
Also known as agatized coral or fossil coral, this forms when silica replaces or fills the empty chambers that comprise unoccupied coral. The original coral is ancient and long abandoned by its organisms, as it can take 30 million years to agatize the limestone structure.