Rockhounding the Rockies: Rock Hounding the Lake George Intrusive area of the Pikes Peak Batholith

A new discovery rock hounding, is it possible? In the fall of 2023,

Looky what I found

I attended a Colorado Springs Mineralogical Society (CSMS) Club sponsored field trip to one of Joe Dorris’s claims. Joe is a local miner who allows Clubs, by appointment, to prospect his claims. I spent the morning prospecting a hillside that many had dug before me. The mineralization signs on the surface of the hill looked promising. I reasoned that if others had dug here, maybe there was something someone had missed or overlooked. There were gemmy shards of quartz and light blue/green chips of amazonite left by others long ago. Some machine digging had also been done. Mother Nature was eroding away a bit of the side of one of the machined pits. I decided to check the old dig. The pit was about 6 feet deep. Near the bottom of the pit-wall I noticed a bit of yellowish clay. The yellow clay contrasted sharply with the greyish/brown surrounding scree. I stuck my pickaxe into the yellowish clay and was soon in a thin seam of microcline crystals. I began an adventure that lasted a few days—could this be the Mother Lode? I followed the yellow clay seam until it intersected with a larger formation of quartz and formed a pocket of crystals. The pocket was filled with smoky quartz crystals that were covered with purplish clay. Unfortunately,

Purplish bottom of pocket still loaded with crystals

the crystals were nearly all broken and deeply fractured. A few single microcline crystals showed a bluish tint to them, so I knew I had amazonite. I probably pulled out a couple hundred quartz crystals that day, but only a few crystals were collectible due to damage. I decided to give this dig a name, and it will hereafter be referred to as the Eclipse pocket. I found the pocket a day before an annular eclipse and came back to the dig a day after the eclipse. After cleaning out the large pocket I retraced my excavation and followed some quartz shards to my left. The broken-up shards of quartz led me into a small, but nicely formed pocket of gems. I got a few complete smoky quartz crystals from this pocket and a couple well-formed, albeit small, amazonite smoky quartz combination specimen.

One of only a couple combos I found

As I finished the day, I sent my good friend Bob into the dig to see what he could find, while I sorted and packaged my finds. Bob pulled out some fluorite and interesting pseudomorphs. I was barely able to keep up with what Bob was pulling out. Pseudomorphs are minerals that replace other minerals, taking on the original mineral’s crystal form. The new crystal has the form of the original. (See Twinning, Polymorphism, Polytypism, Pseudomorphism (tulane.edu)). I was finding quartz in rhombic forms, suggesting to me that the quartz was replacing a carbonate mineral, maybe siderite? At the end of the day, I showed Joe Dorris my finds. He was a bit surprised by the odd pseudomorphs. I returned a few more times to the site with Joes permission and was never disappointed. It seemed I would just finish up one pocket of crystals when another pocket showed itself. I believe there were 5 distinct pockets of crystals. Minerals in all 5 pockets were covered in a purplish clay. While I was digging, as soon as I saw a change of color (reddish brown to purple), I knew I was coming into another pocket of crystals. None of the additional pockets came close in quantity or quality to the crystals I found in the first pocket. All the other occurrences had amazonite, purple fluorite and pseudomorphs of quartz after a carbonate. I found very few smoky quartz crystals as I progressed along the microcline formation/ pegmatite. It seemed like the higher up I dug along the pegmatite, the more faded out the amazonite became. Also, the purple color of the fluorite diminished in intensity. I made sure to show Joe my finds, and he got a share of the minerals. I am a bit stumped on the rhombohedron shaped quartz pseudomorphs. I can’t be sure what the original/replaced mineral was. Similar drusy quartz also encrusted some of the plates of amazonite, making epimorphs of quartz over microcline. The largest unknown is what kind of carbonate was dissolved and replaced with quartz.

Quartz w/ Fluorite ps carbonate

“The most common quartz pseudomorphs are those of calcite, barite, fluorite, and siderite” (https:// www.mindat.org/glossary/ pseudomorphous_quartz). The common theory among local diggers is that the original carbonate was most likely a siderite. I guess I will go with pseudomorphs of quartz after siderite for now. After finishing up digging out the Eclipse pockets, my next project was to clean my finds. The first step was to sort out all the fluorites to clean separately by hand. Next, I took the clay-enveloped minerals to a local car wash for a good soak and spray. After doing a secondary wash at home, I carefully examined my specimens for quality—no sense wasting time and energy cleaning minerals that are chipped or broken. While checking for quality I noticed some very odd crystals. I am used to finding quartz, microcline, fluorite, and goethite, but now I was looking at something different. Time to get out my microscope and take a closer look. I had seen black rod-like minerals before and reasoned this was columbite--Fe (see pic below). Another mineral looked a bit like zircon. After some consultation with subject matter experts, it was determined that the suspected zircons are actually xenotime (see pic below). Finally, I started cleaning the fluorite I set aside earlier. While cleaning clay from the fluorite, I realized that a piece I was cleaning was not fluorite at all but appeared to be barite (see pic below). The barite fluoresces and even phosphoresces a light yellowish-tan under long-wave illumination. Time to check my reference book, Minerals of Colorado, by E.B. Eckel, 1st Ed, 1997. Xenotime, an yttrium phosphate mineral, referred to as xenotime-Y, was first found by R.E. Ziegler in the Pikes Peak Batholith. This was corroborated by E.E. Foord and D.E. Kile (pg. 534). Columbite--Fe or ferrocolumbite was first noted in Teller Feb 2024 CSMS Pick & Pack 17 county by Lazard Cahn (pg. 161). L. Cahn was the CSMS Club co-founder and is the honorary Club president. Finally, barite. According to a Ray Berry communique, small well-developed barite were found associated with smoky quartz, microcline, and calcite in Teller County (pg. 92). No spectrographic or XRF analysis was conducted on any of my minerals. Long-time diggers and subject matter experts of the Pikes Peak Batholith helped me identify my finds. On behalf of all the local Clubs, I wish to give Joe Dorris a hearty thank-you for scheduling and permitting Clubs to organize field trips to his claims. Thank you also for allowing me the extra time and pleasure to dig out and finish a world-class pocket of minerals. Even though it is now the middle of winter, I need to contact our Club’s field trip coordinator up for

more fun during the upcoming rock hounding season!