Other notable & famous feldspar occurences :
Note : Strictly speaking, the term "Feldspar" refers to a large group of tectosilicates such as Albite, Anorthite, Orthoclase and some others. For more information about the more common members of the feldspar group please
Members of the feldspar group may be (apart from quartz possibly) the minerals with the largest crystals in existence. There are several rumours around about sizeable quarries in a single feldspar crystal. An example is the Devils Hole mine, Colorado, where a crystal of the size 50 x 36 x 13 m is reported from. However it is difficult to verify those rumours, even on site, as it is not easy to determine accurately the true extent of a single crystal that large.
Feldspar crystals of one meter and more are a common constituent of pegmatites worldwide and too many to name here. In fact, pegmatites are defined by the gigantism of its minerals, of which members of the feldspar group are among the most common ones. These feldspar crystals usually Do NOT exhibit any freely developed crystal planes, but rather form giant crystalline "feldspar - grains" swimming inmidth of other feldspar (quartz, mica etc.) grains. There are however many noteworthy occurences of freely developed feldspar crystals, which may reach considerable sizes :
- Excellent tabular cleavelandite ( = variety of albite ) clusters up to 15 x 10 cm occur in large cavities in the Rutherford Mine, Virginia and in the Pikes Peak massive, Colorado. Other spectacular cleavelandite crystal "books" are known from the tourmaline pegmatites of Pala and Hercules mine, California.
- Pericline, another variety of albite, is known as a major constituent of hydrothermal alpine fissure mineralization. Many alpine localities with excellent specimen are known, whereas the largest reported pericline crystals, reaching almost 20 cm - came from Gibelmatte in the Binntal, Switzerland.
- Exceptional well crystallized orthoclase crystals are known from many granite pegmatites such as Strzegom / Striegau in Poland and from Baveno in Italy. Another renowned locality are the alkaline pegmatites of Mt. Malosa, Zombas, Malawi, where excellent orthoclase crystals may reach 20 cm and more and often form perfect "Karlsbader" twins.
- Gemmy yellow Orthoclase crystals of up to 10 cm are known from a small locality at Itrongay, Madagascar
- Splendid green amazonite crystals, a variety of the microcline feldspar, up to 40 cm and more are known to occur at various localites such as Pikes Peak, Colorado and recently from Konso, Sidamo Province, Ethiopia.