What Do Agate Rocks Look Like?

What do agate Rocks look like?

Alas, in the natural state they are quite unprepossessing, resembling dull looking potato-shaped rocks to the untrained eye. However, with some experience you will be able to spot one with maybe a translucent, coloured patch, showing the underlying agate through the eroded rock surface. Hunting on a sunny day helps accentuate this feature. Agate-bearing rocks often have a pitted exterior, or maybe a waxy appearance.

At a broken area of rock, agates can often be found in stream beds or on lake shores where the waters tumbling action over the millennia have ground away the rough exterior and polished the agates into bright, easily recognisable gems. Best join a Rock-Hound club and learn how to search for agates from the old timers!

Dendritic Agate

How are agates formed?

It all starts with volcanic rock containing a lot of carbon dioxide and water which bubbles out leaving a “Swiss cheese” texture. When water containing dissolved silica with alkalis percolate through these holes, the minerals are precipitated out slowly in the rock voids, producing those glorious patterns & colours of agates (agate is a form of Chalcedony, which in turn is a form of Quartz, one of the most common minerals on
Earth). The alkali in the solution can attack any iron in the rock, producing bands of iron hydroxide in spectacular forms and combinations with other minerals present in the saturated solution. Agates have also been found in Dinosaur bones, so high temperatures or pressures are not required for their formation, just patience. These agates often maintain the host original shape, after the host (tree, or root etc.) has eroded away, hence their name of “Limb Cast Agates”.

Magma: molten or semi-molten natural material from which all igneous rocks are formed

Some Common Agate Types:

Onyx:

Onyx is a form of agate where the bands are white, alternating with other bands of mainly black, but also of brown or red, depending on the mineral composition of the surrounding area.

Moss Agate:

Moss agate is a Dendritic Agate, looking like it has vegetative inclusions (similar to Amber) but in reality, the Dendrites (from the Greek Dendron – Tree) are usually minerals like oxides of Manganese or Iron, which have percolated into cracks in the agate and then deposited out.

The transparency of the agate allows these dendrites to be seen within the agate.

Moss Agate

Turritella Agate:

Turritella agates are formed from the Turritell shells, a fossilised marine gastropod with an elongated spiral shell or many whorls.

Turritella Agate

Petoskey Agate:

Petoskey agate is an agatized coral found in the Ottawa region of Canada, chiefly around the town of Petoskey, in river beds.

Petoskey Agate

AGATES are truly one of the most beautiful minerals, to be found in a fantastic variety of colours, shades & patterns. When sliced and polished, they are the “Crown Jewels” in any mineral collectors display!

To know about fascinating history of agate, click HERE.

Mike loves rocks! Gems & minerals are Nature’s masterpieces of art that must surely touch everyone’s soul!

Michael Jozefiak

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Created by potrace 1.16, written by Peter Selinger 2001-2019