Chris Tucker Minerals and Gemstones
Specializing in minerals and gemstones from Montana

The Rat's Nest Claim, Custer County, Idaho
Source of exceptional heulandite along with a number of other species.

The scar on the low hill in the foreground is the Rat's Nest Claim

Some distance south of the town of Challis is a low rounded hill that has become famous for producing some of the finest heulandite in the U.S.  Both heulandite-Na and heulandite-Ca occur in geode like vesicles along with mordenite, stilbite, analcime, quartz, laumontite, and calcite.   Crystal lined cavities range from a few millimeters to perhaps a meter in size.  The minerals occur in an andesite flow between volcanic sandstone and siltstone layers.  Since its discovery in 1999, the locality has produced thousands of specimens and many have found their way into the collections of some of the world's top museums and private collections.  The owner of the mine, John Cornish, was kind enough to allow me to visit and help with specimen mining in the fall of 2006.  The number of active and accessible world class localities is rapidly shrinking and the privilege to visit one is something to be cherished.  Thanks John!


Analcime is uncommon at the locality with only a few pieces having been found in seven years of exploration and mining.  Analcime occurs as the usual colorless to milky white crystals.   

Analcime, from near the Rat's Nest Claim, Custer County, Idaho
Colorless transparent analcime crystals that were found on a small hill a short distance from the Rat's Nest.

Calcite is a fairly common mineral at the locality; numerous generations and habits of calcite are known from the mine. Calcite commonly forms large thin platy milky white crystals which often divide cavities and occasionally form the matrix of specimens from the mine.  Blocky dark amber to root beer colored crystals are sometimes encountered entirely encased in later minerals.  Rarely free standing calcite crystals which range from colorless to a pleasing yellow adorn specimens from the locality.

Calcite with stilbite from the Rat's Nest Claim, Custer County, Idaho.
AA large thin calcite covered with scattered crystals of stilbite.  The calcite is 25cm across.

Crystals of heulandite-Ca range from colorless through peachy yellow to a red-orange salmon color and specimens with crystals in the 7cm range are not uncommon.  When scattered about the snow white mordenite they are truly striking.  Heulandite-Ca from the Rat's Nest claim is the finest from any North American locality and has few equals from any locality in the world. 

Heulandite-Ca with mordenite from the Rat's Nest Claim, Custer County, Idaho.
Fresh from the mine and still heavy with matrix, this 25cm wide specimen is studded with numerous 4cm long heulandite-Ca crystals.  This piece now resides in my mineral cabinet.

Heulandite-Na occurs as orange-red microcrystals in small cavities; the area around Challis is considered the type locality for heulandite-Na. 

Heulandite-Na from the Rat's Nest Claim, Custer County, Idaho
A typical heulandite-Na microcrystal, 0.4mm tall.

Sparing amounts of laumontite have been found at the mine where it occurs as the usual slender crystals.

Although mordenite is present in nearly every cavity encountered at the locality, it is rarely of specimen quality.  Cavities lined with fibrous white mordenite have been encountered and by using skilled specimen extraction techniques, some outstanding mordenite specimens have been recovered.   Specimens covered with snow white mordenite along with heulandite are the finest from any U.S. locality.

Mordenite with heulandite from the Rat's Nest Claim, Custer County, Idaho.
Splendid fuzzy white tufts of mordenite with heulandite-Ca.  This little piece was one of the very first pieces I collected at the Rat's Nest claim and it is now in my collection.  11cm across.

Globular encrustations of colorless micro "hyalite" opal is sometimes encountered on the surface of other minerals.       

Quartz is infrequently encountered in cavities at the mine.  When it is encountered, quartz ranges from colorless to a pale amethyst and crystals generally do not exceed a centimeter.  

Quartz with analcime, calcite, and laumontite from the Rat's Nest Claim, Custer County, Idaho.
Colorless quartz crystals covered with small milky white analcime crystals, scattered white crystals of laumontite, and a single light yellow calcite.  Like several of the other pieces pictured here, this one came home with me.  13 cm tall.

Stilbite ranges from colorless to a pale pinkish color and is not a common mineral at the locality although pieces in excess of a foot across studded with sharp crystals 2-3cm in size have been recovered.  Stilbite from the Rat's Nest is likely stilbite-Ca.    

Stilbite, Rat's Nest Claim, Custer County, Idaho
Colorless stilbite crystals on calcite. 5mm across.


Mining for specimens at the Rat's Nest.  The andesite host rock is of such character that an excavator can tear through it with minimal effort.

John Cornish, claim owner, watches for signs of heulandite as the excavator does it's job.

Soon John had a large pile of specimens to trim and pack.  He approved of my specimen extraction skills and turned me loose in the pit with the excavator at my disposal.  After a short time, a number of open crystal lined cavities were exposed extending back into the host rock.  With much delight, I would spend the next ten hours removing crystal covered specimens.

Pinkish orange heulandite-Ca with mordenite. Much heulandite-Na is present in the surrounding rock.

Thick white mordenite with minor heulandite lining a cavity that extends a fair distance into the rock wall.

Thick white mordenite with a platy calcite on the left.  Peach colored stilbite can be seen lining the bottom of the cavity.  John was kind enough to allow me to keep the upper mordenite piece for my efforts at the mine.

Mordenite with heulandite-Ca, Rat's Nest Claim, Custer County, Idaho
Mordenite with heulandite-Ca (and dirt), 25 cm across.  This piece can be seen in the photo above it, where it is upside down in the open cavity.

Several exposed cavities lined with mordenite along with heulandite, stilbite, and calcite.  Note the pick for scale.

Here John is starting the task of trimming and packing specimens.

With the sun setting the temperature is dropping and John is still packing.

Exceptionally fine mordenite with heulandite specimens packed with aluminum foil.  The foil allows for tight packing with very little movement and is far superior to the normal plastic and paper packing materials in this regard.

heulandite on mordenite, Rat's Nest Claim, Custer County, Idaho
I thought that this piece with it's 6cm heulandite on mordenite was rather attractive so I grabbed a quick shot of it while John was packing.

With the delicate mordenite specimens packed away, John begins trimming and packing the heulandite pieces from this years mining efforts.

Now that this years mining is finished, the cut is filled and a new bench is cleared to the right.  John will mine the newly exposed rock in the next year. 





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