Gate to the main pit
Claim jumpers digging on the alluvial bench
Washout after July rains
Topaz Mountain Gem Mine
Mining Season 2006 Part II
This page describes the topaz deposit at Topaz Mountain Gem Mine and our present mining operations. We plan to use mechanized equipment and jigs in the near future.
Deposit: The most productive area at Topaz Mountain Gem Mine is a relatively small area of about one half acre. This is an alluvial bench of material deposited in somewhat of a fan shape at the foot of some rather intimidating cliffs. Part of the deposit has come from debris washing from the adjacent steep hillside, and some was deposited by the ephemeral stream to the west. Those of you who have been by the claims recently have witnessed the development of new gravel deposits formed by the flash flooding this past July and August 2006. The fence line is buried to within a foot of its top. I know of one person who benefited from the flash flood as he found a magnificent topaz in the road.
Gate to the main pit |
Claim jumpers digging on the alluvial bench |
Washout after July rains |
To date, two major pits have been opened in the primary deposit, one on the north end and one on the south. Despite the signs and gate, the material between both pits has been sampled in several spots by claim jumpers. One rather large hand-dug pit lies between the two end pits and was started by claim jumpers. Eventually, it has expanded to about 30 by 30 feet. I am responsible for only a small portion of this. (I have now offered a reward for the successful arrest and conviction of anyone caught claim jumping.)
The alluvial deposit is also an unusual feature. The area is heavily overgrown due to the abundant moisture from frequent afternoon showers. As a result, plant roots extend deeply into the deposit. Secondly, huge boulders, some the size of an SUV, are embedded throughout the alluvium. (Some of these boulders do contain pegmatitic features, but thus far, I have found no cavities.) Between, the boulders is an assortment of all sizes of rock solidly cemented together with clay. Sorting is very poor to non existent.
Deposit Profile: The alluvial gravels may be as deep as fifteen feet in places; however, it averages six feet deep and is anything but gravel. The rich, black topsoil, heavily matted with roots and vegetation, averages a foot thick. Below this, an orange-red subsoil is encountered, also about a foot thick. This grades into heavily cemented red gravels which are intermixed with grayish or yellowish clays. This layer varies in thickness from a foot to five feet. The clay zone grades into larger, fractured decomposing granite in a zone up to two feet thick, until the granite becomes solid bedrock. The deposit consists mostly of rounded granite boulders intermixed with cobbles, gravel and sand. Most of the sand and gravel is cemented tightly together by calcium which has leached downwards. Very small "pockets" of workable gravel and sand occur in and around the boulders.
 Boulders down to bedrock |
 Scott Dorris working a small gravel seam |
 Jon Voelter holding up a nice gem topaz |
This alluvial bench, differs from other nearby benches. Other nearby benches and alluvial fans are composed mostly of shattered granite fragments disseminated through mostly loose, granitic soil. The soil horizons are not well differentiated and no sorting is present. Even so, some topaz crystals also occur in these benches, but considerably fewer than the Topaz Mountain fan.
Nature of Deposit: Topaz is found from the surface down to the bedrock. Most of the deposit yields rounded crystals and fragments, but there is an occasional sharply terminated crystal devoid of abrasion (about one in fifty). Thus far, there is no pattern to this weathering. I have found sharp crystals from within the black soil to well down to bedrock where I've found them amongst completely rounded topaz. Most of the topaz pieces and crystals average 20 carats. To date, I have found several, water-worn crystals that exceed 350 carats in weight. I've seen one over 700 carats. The largest sharp crystal I've found is about 250 carats. However, larger ones than this have been found in crystal pockets within the surrounding granite cliffs.
Present Recovery Methods: The first step in recovery is the old-fashioned pick and shovel. I start from the surface and work downwards until impenetrable bedrock is encountered. The first foot is generally easy because it consists mostly of topsoil and subsoil. After this, the alluvium becomes cemented and with each swing of the pick, only about an inch or two can be pried loose. Frequently this material is so hard that the pick breaks through a cobble rather than knocking it loose. Whatever chunks of gravel and clay are loosened, I allow to fall the floor of the hole. While I continue prying, I'm further crumbling the chunks under my boots. When I have enough loose material, I shovel it into the screening system I built. When large boulders are encountered, I enlarge the hole, rather than undercut the boulder (dangerous business), until I can remove it. Some are simply too large to haul out by myself, so I roll them to a side of the hole. Gravel is often cemented to the boulders so I remove this with a chipping hammer. After a boulder is removed, there is also generally a small amount of gravel between it and the next. I remove this usually with a screwdriver, but sometimes a sharp rock hammer or small pick works equally well. Occasionally topaz are spotted in the gravel between the boulders.
Presently I am using a dry screening system which I built. After mining for sapphires in Montana and Idaho for a number of years, I reasoned the topaz could be recovered using a similar screen, but with some minor modifications. The shaker I built consists of two nested screens, the smallest having a three-eighths inch size opening, the upper screen having a half inch. These are set on two "rocker bars" to enable the screens to be rocked and shaken.
Since the ground is generally moist and has a high clay content, it takes some effort to work the gravel through the screen. I frequently rub it through the screen by hand (wear gloves). Fortunately, clay and dirt tend not to stick to the topaz and when rubbing the material through the screen, the clay rubs off any topaz, exposing them. I screen everything. Usually nothing is found in the topsoil or subsoil, and this is screened quickly. On occasion, I do find topaz in this layer. One of the best I've ever found came from the contact between the topsoil and the subsoil. On rare occasion when the gravel is dry, I can quickly and easily screen it. It's also easy to spot the topaz when it's dry. If the ground is particularly muddy, I've found it best to allow it to dry before attempting any screening. Some people simply wash the gravel at this point, however, and then search for the clean topaz. Topaz's high refractive index makes it easy to spot when washed.
I can process about eight shovels of gravel per screening. Keep in mind, this gravel is painstakingly collected from the spaces between the boulders. There isn't much. On average, I find one stone per every two screens (16 shovels of gravel). That isn't much. It's easy to go for three or four screenings before finding a single stone. Other times, two or more stones will show up in a screening. My record so far is one large topaz in the upper screen and three small stones in the lower. When I have help, one person usually operates the screen while the other picks at the gravel. Three people make the operation ideal.
 Baxter busy keeping the bears away |
 Tim Dorris using the shaker system |