Sepiolite is an important speciality clay used mainly for its gelling and absorbing properties. More information on sepiolite can be found here.
The Pioche Sepiolite Project is located close to the historic mining town of Pioche in Lincoln County, Nevada. It lies within 4km of US Highway 93, from which it can be accessed by a network of 4WD tracks, and 47km from rail at the town of Caliente, Nevada.
The Project was acquired at low costs by claim staking.
Exploration
Originally documented as a sepiolite occurrence in the 1970s, the occurrence was relocated by SRM in 2021. In 2022 Tolsa ISA Inc., a US subsidiary of Spanish sepiolite producer Tolsa SA, entered into an option to purchase agreement with SRM and explored the property until December 2024 when the option period expired.
In summer 2022, Tolsa completed a programme of detailed geological mapping and trenching. This identified two (possibly three) sub-horizontal and extensive sepiolite beds outcropping intermittently along the margins of two mesas now know as the West and East Mesa areas. A silica rich caprock tops the sepiolite at the discovery location forming low mesas and flattened ridgetops.
Outcrop is generally poor throughout the claims due to a covering of quaternary soils, sands and gravels.
2023 Drilling Campaign
In Summer 2023, Tolsa carried out an auger drilling programme. Twenty holes with the prefix SR- were completed for a total 930 ft of drilling and an average per drill of 47.6 ft.
Drilling was carried out using an auger rig mounted on a Ford F550 truck, owned by Tolsa USA Inc, and hauled from Casper WY to the work area. A total of 166 samples were collected on 5ft auger stems with sample intervals determined by on textures, appearance, colour, and lithological differences. From this a first stage 40 samples were submitted to Tola in Madrid for initial screening.
2024 Drilling & Trenching Campaign
In order to acquire larger samples with better depth control and reduced downhole contamination, a programme of sonic drilling was carried out in July 2024. The drilling was contracted to Harris Drilling and achieved excellent recovery of 6-inch diameter core-like samples.10 holes were completed, prefixed AF-.
During the 2024 drill programme a number of excavator pits were also sampled.
Sample Testing Programmes
Tolsa has provided Sunrise with a database containing sample testing results for various mapping, trench and drill samples.
The testing, carried out in 2023 and 2024, included:
Of these the determination of viscosity is a critical measure to determine the gelling (viscosity modification) properties of sepiolite which impart a higher commercial value.
The data provided has been reviewed by Sunrise and Tom Powell.
The best and most consistent viscosity results come from the 2022-2023 exploration in the East Mesa area notably in Trench 10. The nearest drill hole, SR-14-2023, some 140m away, intersected extensive sepiolite with the second highest viscosities.
Hole SR-25, 400m further to the southeast across the same East Mesa as Hole SR-14-2023 and Trench 10, also contains extensive sepiolite beds with higher viscosities.
Sunrise SR Minerals had expected the 2024 drill holes to follow up on the earlier results but the 2024 drill holes were drilled further afield and to the south-east as shown in the accompanying map, and no follow up holes were drilled in the West Mesa Area. The 2024 drilling programme seems to have been designed to scope out the sepiolite deposits over too wide an area.
Typically, sepiolite deposits in the Amargosa Valley are drilled on c.30m centers as opposed to the c.300m spacing drilled by Tolsa. The current drill spacing at Pioche is far too wide for effective correlation of sepiolite beds.
Tolsa has drilled only one hole in the West Mesa discovery area and both the East and West Mesa areas are priority areas for resource definition.
The sepiolite morphology at Pioche is similar to Amargosa valley sepiolite and will likely require mineral processing techniques similar to the Amargosa Valley deposits – e.g. milling, sizing, extrusion etc. The Protocols for sample preparation and viscosity testing used by Tolsa most likely based on Spanish sepiolite, do not appear to reflect this processing requirement and so may not be appropriate for Pioche Sepiolite.
No testwork is reported by Tolsa to evaluate salt-water viscosity. However, this is a key property for the US oil drilling market where sepiolite is used in drilling muds to gel saltwater and raise the drill cuttings, a use for which Amargosa Valley type-sepiolite is well suited.
The timing for new entrant to the sepiolite market in Nevada is favourable. Increased oil/gas well drilling is expected under Trump administration. At the same time the only US sepiolite producer in the Amargosa valley is under existential threat as it is unable to replenish reserves due to the encroachment of Areas of Critical Environmental Concern.
About Sepiolite
Sepiolite has unique characteristics, is scarce, and there are very few commercial deposits in the world.
It is a non-swelling, lightweight, porous hydrous magnesium silicate clay. It possesses a high surface area due to channels in the crystal lattice that gives it a structural nano-porosity. Its unusual crystal shape also adds to the internal porosity and gives it a light weight.
Sepiolite’s high surface area and porosity account for sepiolite’s outstanding sorption capacity. Just 20g of sepiolite can have an internal surface area equivalent to that of a football field and sepiolite can absorb more than its weight in water. The largest market globally for sepiolite is for use in light-weight non-clumping pet litters where it has superior properties compared to other clays used in this application.
Sepiolite is also used extensively in agriculture as a slow-release absorbent and adsorbent carrier for chemicals and pesticides and in animal feeds as a binder and carrier for nutrients and growth promoter. It is also used to decolour vegetable and mineral oils.
The unusual crystal shape means that sepiolite is not easily flocculated and so it’s colloidal properties make it useful as a suspending agent in paints, medicines, pharmaceuticals and cosmetics.
Sepiolite, unlike other clays, is not affected by salt water and so sepiolite drilling muds are used in oil field wells where brine formations are a problem. It is also the only clay that is stable at high temperatures and so is used in drilling muds for geothermal wells.
Sepiolite is usually mined by open pit methods and is processed by drying, grinding and screening and may undergo further treatments and transformations depending on the market.
