New Mexico Mineral Symposium — Abstracts

The first unusual crystal to look at is "pagoda" quartz from Young's River, Astoria, Clatsop County, Oregon. This is part of the Columbia Plateau basalt flow. Pagoda quartz was formed by calcite oriented on the original quartz crystal; then at a later date these calcite crystals became pseudomorphs of quartz after calcite. The girdling bands of quartz have no relationship to the original crystal.

The next crystal to look at, very closely related to the first, is "cut quartz" from Dalnegorsk, Russia. Here the quartz and calcite formed at the same time; later the calcite was dissolved away leaving only the quartz. Another locality where "cut quartz" was collected by the author in May 2005 is near Story, Montgomery County, Arkansas. This is a pay-to-dig open pit claim of G. W. Johnson. The cut quartz crystals are found in clay between sandstone layers.

Faden quartz is another unusual crystal to look at; faden is German for "thread," which appears to run through the crystal. This faden is formed by a tectonic fracture of a quartz crystal and the subsequent widening of the fracture. During this time just enough quartz-forming solution entered the fracture to form the faden. This consists of tiny oriented crystals of quartz that appear white because of water and gas inclusions. Some noted localities for faden quartz are Waziristan, Pakistan; Saline County, Arkansas; Graubunden, Switzerland; and Quebec, Canada. Another locality that was brought to my attention in 2002 by Dwaine Edington is Chihuahua, Mexico. These crystals are micros seldom more than 2 or 3 mm in size. They formed in the confines of small quartz-lined geodes; much more work needs to be done on this occurrence of faden quartz.

Gwindel or twisted quartz crystals are one of the more unusual quartz. They are one of the most studied without any conclusion as to how they were formed. There are as many hypotheses as authors on this subject. We know something kicked the crystal normal growth pattern out of whack. Normal growth pattern for quartz is a spiral around the "c" axis, with rhomb growth 3-5 times that of the outer faces. However, the spiral growth of a gwindel is around one of the "a" axes; latest hypothesis is it is due to the chemistry of impurities. Noted localities for gwindels are the Dodo mine, Tyumen Oblast, Russia, and the northern part of the Alps, Switzerland.