New Mexico Mineral Symposium — Abstracts

The term amazonite or amazonstone as used in this article refers to the light to dark green variety of microcline feldspar. Amazonite and smoky quartz crystal groups have been collected in the Crystal Peak area since the 1800's. Crystal Peak, elevation 9637 ft, is located approximately 3 mi north of the Lake George-Florissant area in Teller County, Colorado. In 1867 Ovander J. Hollister referred to the location in his book, The Mines of Colorado. Since then the area has been collected extensively and is world famous for amazonite-smoky quartz crystal groups and associated minerals.

The amazonite and associated minerals occur in pockets in pegmatite lenses and dikes that are classified as the simple type. The pegmatites were emplaced at a shallow depth in the Pikes Peak batholith and surrounding metamorphic rocks. The contact between the pegmatites and the surrounding rocks is usually sharp.

The Ten-percenter mine is located on the northeast side of Hackett Mountain just northwest of Crystal Peak. The mine has been worked from upper, middle, and lower excavations. The upper level has yielded fluorite on smoky quartz, amazonite, and columbite-tantalite. The middle level has produced amazonite, smoky quartz, and small fluorite cubes. Good smoky quartz and amazonite crystal groups have come from the lower level.

The Ten-percenter mine has produced the following minerals from the pegmatite pockets.

APATITE occurs as cream to dark green crystals up to 4 inches. The crystals occur as singles and groups and most are untwinned.
BASTNAESITE is thought to occur as microcrystals but it has not been positively identified.
CLEVELANDITE (ALBITE) occurs as white- to cream-colored crystal rosettes associated with amazonite.
COLUMBITE-TANTALITE is found as black terminated crystals up to 1 inch.
FLUORITE occurs as purple cubes up to 1 inch in groups and on smoky quartz.
GALENA is found as blue-gray metallic masses with amazonite. PHENAKITE occurs as small colorless crystals.
QUARTZ occurs as clear to smoky crystal shards, doubly terminated crystals up to 14 inches, and as crystal groups.
TOPAZ occurs as colorless to brownish-red, euhedral crystals that sometimes show slight etching.

Don Smith recounts the discovery of the "key-hole vug."

Having spent the first seven weeks of the 1986 mining season following numerous small pegmatite lenses in the center cut of the mine, I decided to give this area a rest and prepared to move my operation back to the originally discovered lower cut. On Monday, 9 June, I fired up the dozer, walked it down to the lower cut, and after a short lunch break was ready to begin exploration work. This cut has been a good producer of smoky quartz and amazonite specimens in both singles and combinations every season since 1972. It has good exposures of pegmatites and has been used as a study area for geologic mapping during the summer.

I started working my way towards the apex of a small, uplifted, dome-like structure that to me was not normal to the slope of the hill above the cut. It was around three o'clock in the afternoon, and I had just completed a final cut and back-drag of decomposed plates of diorite and granite from the west face of the cut. As I was backing up, I spotted a long thin quartz vein in contact with a six- to eight-inch vein of Pikes Peak pegmatite.

Shutting down the dozer, I gathered up some hand tools and started to expose the two veins. After a few minutes work I had exposed an eight-inch quartz vein contacting a twelve-inch pegmatite vein. The quartz vein was pinched off just shy of the diorite, but the pegmatite vein swelled in width and was arching down under the diorite on a 30 dip striking southwest.

In order to get through the quartz vein, I had been using a long steel drill bit. All of a sudden the point broke through into open space. I moved about twelve inches to the right and started another hole so that I could use a bar to remove a section of the quartz vein. Once more I broke into open space. I asked Dean, a friend helping me, to get a small mirror from the tool box in the jeep so he could reflect the sun into one hole while I peered into the other. As I looked through the hole, I could hardly believe what I was seeing in the reflected sunlight. I was looking inside what appeared to be a large hollow hemispherical cavern. I was unable to make out the top of the ceiling but was able to see a washed level of fill with several large, red iron-stained, quartz shards lying on top.

Using a chisel, hammer, and pry bar we enlarged the first hole so that I was able to get my hand and arm through it. Putting my arm in up to my shoulder I felt around in the loose clean fill, recognizing by touch the shape of a quartz shard. In order to get rid of some large blocks of granite at the bottom of the cut, I made up one stick of powder and packed it into the base of the granite. After the shot went off, we found that it had gassed through cracks in the granite plates such that the plates were readily pried loose. In a short time we had them rolled into the dozer bucket and quickly had the cleanup work completed.

Enlarging the small hole we had made in the quartz vein, we soon had a small door opening into a large igloo-shaped open vug. Inside, lying on top of very clean washed fill was a six-inch-diameter smoky quartz crystal, tens of other quartz crystals, shards, and one large plate of amazonite that we later found weighed 45 lbs. By enlarging the door opening a little more, I was able to crawl inside and sit upright on top of the fill. The north half of the ceiling was composed of Pikes Peak pegmatite and in the center was a six-inch-wide quartz vein striking northeast and dipping 75. Because it was getting late, we removed a few more quartz crystals and shards, sealed the door with the dozer blade, and called it a day.

Returning early next morning we started the recovery work. I thought we had 12 inches of fill to remove, 15 at the most, before we reached the final bottom of the pocket. It would take another 5 days to find out how wrong I was about the final depth to the pocket floor.

The first really full day's work on the recovery produced over 200 smoky quartz crystals of which 80% were doubly terminated. Numerous singles and twins of amazonite were recovered; a good share of these had rosettes of clevelandite on them. All the amazonite was a good deep-green color, sharply terminated, and fracture free. Two more large ceiling plates of amazonite with clevelandite were recovered; one weighed 65 lbs and the other 192 lbs. Thirteen ceiling plates in all were recovered, the largest weighing 300 lbs. Three large floor plates were recovered, averaging almost 200 lbs each. At the end of the week, working 12- to 15-hour days, we finally reached the floor of the vug. The distance from the apex of the ceiling to the floor was 92 inches. After all the fill material had been removed from the "key-hole vug," the empty vug measured 92 inches high, 7 ft wide, and 6 1/2 ft long. Almost 1800 pounds of choice specimens were recovered.

On site during recovery work were Reinhard A. (Bud) Wobus, professor of geology at Williams College in Massachusetts, Miss Sara Finnemore, undergraduate student, and Eric Wobus, son of R. A. Wobus. I was honored by having Eugene E. Foord, geologist-mineralogist at the USGS Denver branch, and John S. White, Smithsonian Institution, Washington D. C., on the site during recovery work. Gene: "Only once in fifty years is such a vug found." John: "The material recovered from the vug was just phenomenal". All excavation and recovery of the vug's contents were documented on tape, with photographs, and by measurements.