 |
|||
|
|||
|
Copyright
Precious Opal from the
Northern Lights ClaimWe are exploring and trenching 6000 feet up on a flank of the Whitesail Mountains in northwest British Columbia. The Northern Lights Claim is located approximately 90 air miles south of Houston, BC and access is by helicopter. This is one of the few alpine locations in the world where precious opal can be found and paying attention to the task at hand can often prove difficult when blizzards and howling winds are trying to knock you down. Our extremely short weather window lasts from late July to early September and snow can fall anytime. Frozen fingers and toes are the price paid for BFDs (bug free days) as sunshine and calm winds signal the hordes of bloodsuckers from their hiding places to have their lunch. We have only been scratching this property with hand tools, but finding visible precious opal in surface outcrops over a 5 sq. km area has captured our attention.
GeologyVolcanic hosted opal deposits are believed to be associated with hydrothermal activity. At the Northern Lights claim, precious opal occurs most commonly as open space fillings in the matrix and vesicles of clasts in the volcanic lahar (debris flows) and lapilli-tuff units of the Tertiary-aged Ootsa Lake Group. It also occurs as amygdules in massive flows. The dominant opal bearing lithologies are the debris flows with minor amounts in the lava flows and ash fall tuffs.
Opal types and qualityCommon opal of all colours, many types of agates and even one agate with a line of precious opal inside occur in close proximity. Geological theory does not explain how one vesicle can be filled with bright precious opal, the adjacent one empty and the occasional empty vesicle shows an inside surface that flashes with precious fire. Celadonite and zeolites are present which somehow indicate a favorable geological environment.
Precious opalThe precious opal matrix material represents our biggest volume of production at present. In appearance, it shows small flecks of all colours distributed throughout various matrix hosts. The strongly vesicular hosts or matrix types can range from a dense hard black basalt to softer brown porphyritic andesite and to grey, even reddish colour material. Vesicles filled with precious opal may account for over 25 per cent of the volume of the rock. Kevin L. Smith, a renowned carver, likened the matrix material to dinosaur bone in his description of the material. Although sometimes the host volcanic material will take a good polish, sadly the majority of the matrix material produced so far has been too soft for daily wear and will require stabilizing. After stabilizing, the matrix material exhibits good colour and is suitable for spheres, carvings and jewelry grade cabochons.An amazing dacite dike was the site of the original discovery of precious opal in the Whitesail range. This prominent vertical feature stands over 20 feet tall and 3 feet wide in places where it cuts through the opalized country rocks. The prospectors have named it the Great Wall, as it resembles closely its namesake, snaking across the property in a distinctive spine.
Carving and cuttingCutting these various types and grades of opal presents unique challenges and several cutters and carvers are using their skills and knowledge to achieve good results. Techniques such as doublets work well but natural stones are tricky due in part to the extreme environment and the deep surface weathering. To date mining is limited to the surface or near surface material. We believe that as trenching proceeds deeper less fractured opal will be recovered.
ExtractionPermanent snow pack covers much of the terrain. Tenacious alpine plants cover any marginally habitable ground so outcrops and exposure of bedrock are minimal on the top. The top is relatively flat with the sides very steep and horizons of red, grey and black units can be followed around the flank and appear to be continuous. With a flat glaciated top and various coloured layers, our best description is that it resembles a chocolate layer cake. The precious opal at this locality occurs in over 20 places in nodules, seams and as matrix-hosted material. However, safely trenching or extracting material is a different matter.Our first trench was named Zona Rosa for the red colour of the basalt. It proved an exercise in the excavate and tumble method of mining. Luckily, a flat bench 100 yards below stopped the boulders on their downward journey. It is difficult to forget the experience of tumbling stove-sized boulders weighing hundreds of pounds down a snowfield onto a flat. A member of the team would be hunkered down in a safe place noting where the boulders landed. Pieces that survived the tumble were given the sledge and chisel treatment, and reduced to gravel piles. Many bright precious opal specimens were found here but the action of freezing and thawing fractured most of the near surface material. As this trench progressed into the steep slope, the uphill wall became hazardous and digging was abandoned. From another very steep site located directly above our fly-in camp, we would send boulders the size of automobiles skidding down 600 feet of snowfield often to have them land within an easy walk from camp. This type of opal mining is not for the faint of heart. We have recovered water worn precious nodules from small streams and consider them a real treat. Placer techniques have proven productive in highly weathered areas and make an attractive choice for those infrequent sunny days. Screening pea gravel for flashy nodules by a bubbling alpine creek is a very special experience.
Prospecting challengesProspecting for precious opal in an alpine environment presents peculiar challenges and conditions. A float trail will often descend where snow and gravity have chosen. Following the float uphill until it flashes in place is always a productive way to prospect. Steep snow slopes are to be avoided without proper gear and the scree slopes and ravines provide plenty of challenge on the edges. Strongly rooted shrubs and bushes are an alpine prospector's best friend but gloves, walking sticks and even kneepads all have their place in your backpack.In this pristine environment, the many permanent snowfields provide our fresh water and a highway system. Refrigeration in camp is never a problem. Sunshine melts the snow at the rate of an incredible 2 feet per day and the resulting layer of corn snow has provided more than a few quick descents sitting on a raincoat. With your feet out front and a pickhead clenched firmly in your grip a downhill slide at the end of a hard day can lift your spirits quickly. We cut trail where needed and found that even the resident wolves immediately started to use our trail in one particularly steep area we call the Razorbacks. Crossing the Razorbacks is perilous to the extreme and often we see mountain goats peering up at us thinking cleverly, "two legs bad /four legs good". We agree completely with their wisdom. Two legged visitors are scarce but the local critters add plenty of character to the site. Mountain goats, marmots and ptarmigan are common sights and have proven to be good neighbours. The wolves and the resident King of the mountain, a huge grizzly, leave us alone and tolerate our short intrusions into their territory. Whistlers, commonly called marmots, live right next to our camp and have trails and burrows all around us. They are curious as well as frightened by tall moving objects and their shrill whistles are echoed throughout the mountain by their nearest neighbours as an effective early warning system. The sprinkling of their jaw bones with their long incisors all over the alpine suggest that the wolves are serious and efficient at hunting these mountain piggies. Many marmot burrows are dug under huge boulders in order to avoid their most terrifying predator, the grizzly bear. Huge excavations where boulders the size of refrigerators have been torn out of the ground attest to the grizzlies desire for a whistler meal. This last season we enjoyed fresh baked bread in camp and when a big blue grouse noticed the other alpine birds munching down crumbs in our camp he moved in as well. The many ptarmigan don't seem to mind human company but keep our canine mascot, a miniature wiener dog named Misty, running in circles. Misty, whose ancestors were bred to hunt badgers, chases whistlers and nearly met her demise down a marmot burrow one season. After she chased one down a hole it turned on her and tore big strips off her nose and head. The poor beat up dog limped back to camp and remained comatose next to the woodstove for close to 3 days. The lesson did not last though because after a full recovery she was even tougher on them. Mountain goats range freely over the entire property and some walk right up to us while we are having lunch. Their stray tufts of dense white fur clinging to rocks are often mistaken from afar as white opal. The nannies and kids gather in small herds and after feeding on whatever they can find, generally seek safety in the cliffs. The billys travel around a bit more and all the goats have favorite dust baths and mineral licks on the mountain. Their ability to climb and descend seemingly vertical faces is astounding but their bones do show up as well. Each year a lone bull moose has walked past our tents on his way through camp. Mountain cariboo also pass through the area and shed their horns. Strangely, porcupines are encountered up high where no twigs or suitable vegetation is evident. We believe they are teenagers kicked out of the good foraging areas down in the trees. Their teeth marks on ancient 4x4 claim posts show their hunger and need to chew but with no trees to climb, they become easy targets for predators. Frequent southern visitors to our mountains are the beautiful ruby red and emerald green rufus hummingbirds. As they follow the glorious blooming alpine flowers north, they often buzz around our heads, attracted by brightly coloured headgear or backpacks. Their loud buzzing as they circle your head can be startling but their friendly antics leave smiles all around.
Equipment and other challengesAs access is by helicopter, we have had to rely on hand tools and portable gas powered saws and drills. We use a wheelbarrow and an alpine rickshaw outfitted with mountain bike wheels for moving loads. These have proven very efficient and this season we flew a small excavator in to assist with trenching. This digger weighs 850 pounds without its stabilizers and counterweights and flew straight and true like a dragonfly after pick-up by the chopper. Moving this lightweight machine across snow, mud and gravel is accomplished by extending the boom and bucket then lifting the front stablizers and rolling forward on the back wheels as the boom is retracted. The speed and agility of this digger is amazing and future plans include mounting a hydraulic jackhammer in place of the bucket. Alpine trenching has taken a quantum leap forward as a relatively inexpensive Bell 206 can be used instead of the pricier heavy-lift machines.
Potential explorationBritish Columbia has a wealth of mineral resources and because of its rugged terrain, much of the province has remained unexplored or prospected. That precious opal deposits occur in BC is relatively unknown but recent discoveries are about to change that. Singular specimens have been found from the southern Okanogan area up to northwest British Columbia. Two other properties, notably Firestorm Opal of Burns Lake and Okanogan Opal of Vernon, BC have produced beautiful specimen and jewelry grade material. These volcanic hosted precious opal deposits indicate that closer inspection of all common opal and agate areas may yield further discoveries and significant attention is warranted. From our experience, getting your nose down to ground level is required and recommended to all opal prospectors.
This article may not be copied, distributed or reprinted in any form without the author's permission. To contact the author, please use the e-mail address provided. If you are unable to contact the author, please contact the Canadian Rockhound. Authorized reprints must acknowledge the author and the Canadian Rockhound. You may also contact the author using the address below. Please do not send unsolicited mail.
Randy Lord,
|
||
 
Copyright © 2000 Canadian Rockhound
Back Issues |
News & Events |
Junior Rockhound |
Resources
|
|||
