Friday, November 5, 2010

Topaz Crystals from the Petra Placer, Tarryall Mountains, Colorado

The Tarryall area in Park County, Colorado is known for the exceptional topaz specimens discovered there. Topaz in the Tarryall Mountains forms in cavities of various sizes in pegmatites (coarse-grained granite).

Topaz with blue tint from Tarryall area.
The Hayman Fire of 2002, the largest forest fire in Colorado's history, has been a major factor in the discovery of new topaz deposits in the Tarryalls. Frequent summer rain storms form gullies that uncover topaz-bearing pegmatites that provide new sites for collectors to work. Additionally, afternoon thunderstorms wash away gravel and reveal topaz crystals on the surface.

The Hayman Fire made topaz hunting easier.
Pilot Peak is in the background.

East of the China Wall (a prominent granite landmark in the area) Mutakat Road (Forest Road 211) winds it way near an area where a number of mineral claims are producing gem topaz. The Petra Placer is one of these claims. Rich Fretterd, a member of the Lake George Gem and Mineral Club, staked the Petra Placer in April, 2004 after discovering a number of fine topaz specimens. The name of the claim comes from the Latin word petra, meaning rock or stone. The Petra Placer is southeast of Pilot Peak (SW1/4 Ne1/4 Sec. 12 T. 11S, R72W).

A Petra Placer topaz crystal.
The specimens from the Petra Placer are remarkable for their large size and clarity. A number of topaz crystals are just below the surface in gravel deposits. Petra Placer specimens have a blocky, prismatic crystal habit. Some of the prism faces are slightly etched. Most specimens have a bluish-tinge. Anhedral (lack crystal faces) specimens are faceted into gems and euhedral (have crystal faces) specimens make their way into museums or the mineral cabinets of rock hounds.

Sifting gravel yields topaz.
As a result of the Hayman fire, the topaz crystals of the Petra Placer have been revealed. Digging in various parts of the claim continues to yield excellent specimens. The Petra Placer is now a significant Colorado topaz locality.
Clear topaz crystal from the Petra Placer


Topaz crystal perched on smoky quartz.
 

Crystal specimen with etching.


End of a good day of prospecting


© Cripple Creek Center for Earth Science Studies

5 comments:

  1. The photos are superb - mouth watering. It would be helpful if the crystal dimensions were also given.

    ReplyDelete
  2. How do you find public places to go digging for crystals/gems in the Tarryall area?

    ReplyDelete
  3. I get a National Forest map that shows all of the roads and trails. This is the best source to get you to public lands. If anyone has a topaz or other mineral claim they will have it marked so that you will know to stay off, otherwise the land is open. A good thing to do is to call the National Forest office to see what their local rules are.

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  5. Are there publications about Topaz from Colorado?

    If so, I would like to add some links to our site with "Literature about Topaz":

    http://www.meelis-bluetopaz.com/topaz-literature.html

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