Property Description

Cecilia, Fronteras, Sonora

Cecilia Project


COMMODITY: Gold and Silver


DEPOSIT TYPE: Low Sulphidation Epithermal Au-Ag Rhyolite Flow Dome Complex

LOCATION: Sonora, Mexico

SIZE: 6,897.3075 has

STATUS: Drill Permitted, Available for Option


The drill permitted Cecila project, located 40 km southwest of the Mexico-U.S.A. border town of Agua Prieta, is easily accessed by paved highway and dirt roads and covers 6,897.3 ha within the municipality of Fronteras, State of Sonora, Mexico.  The world-class open-pit Cananea porphyry copper mine is situated 48 km west-southwest of Cecilia.  Deposit analogs include the La Pitarrilla deposit containing 526 million oz Ag (Measured + Indicated, SSRI website) and Fresnillo’s San Julian silver mine containing over 230 million ozs Ag, both located in Durango, Mexico



As many as 30 abandoned exploration adits, small underground galleries and surface prospect pits are distributed over the upper slopes of Cerro Magallanes, believed to date back to the early decades of the 20th Century. 

By around 1981, the Consejo de Recursos Minerales (CRM) initiated a project at Cerro Magallanes.  Over a 3-year period CRM carried out a comprehensive exploration program, including:

  • 896 km2 squared of regional mapping
  • 635 surface rock chip samples
  • 14.3 line kilometres of induced polarization
  • 1,412 m of underground mapping
  • drilling of 4 diamond drill holes totalling 732.3 m
In April of 1994, Cambior Exploracíon S.A. de C.V. entered into an option-to-purchase agreement with the DGM for the project. Under the agreement Cambior was obligated to incur exploration expenditures totaling $700,000 in the first 18 months, $1,900,000 in the second 18-month period and $5,400,000 during the following 36 months.  Cambior terminated the contract at the end of the first 18-month term, their work is summarized below
  • 9 km2 1:2,500 orthophoto and topo map with 5 m contours
  • 6 km2 of geological mapping at 1:2,500
  • 12.85 line kilometres of induced polarization, ground magnetic survey over 2.8 km x 2.4 km
  • 666 surface rock chip samples
  • 1,200 m of underground mapping, 388 underground rock chip samples
  • drilling of 19 diamond drill holes totalling 3,817.6 m
Minerales El Prado S.A. de C.V. (“El Prado”), the Mexican subsidiary of Chesapeake Gold Corp., was the next company to acquire the project.  El Prado conducted rock sampling programs between 2004 and 2009 and collected a total of 738 surface rock chip samples.  From 2009 until 2013 essentially no work was done.
In February of 2013, Precipitate Gold Corp. entered into an option agreement with Gunpoint Exploration Ltd., who then controlled the La Cecilia project.  To acquire 100% of the project, Precipitate was obligated to pay Gunpoint in three installments a total of $400,000 cash and issue a total of 525,000 common shares over a 2-year period. Minera Pendiente conducted due diligence work on behalf of Precipitate Gold, collected 43 surface rock chip samples and resampled and analysed 35 samples from 2 drill holes.  Precipitate decided not to finalize the agreement with Gunpoint Exploration.  
In January of 2017, Riverside Resources Inc. purchased the Violeta concession from Millrock Resources Inc. for C$10,000, 100,000 Riverside shares and by granting Millrock a 0.5% Net Smelter Return royalty. Riverside concurrently signed an option to purchase agreement with Gunpoint Exploration Ltd. to acquire a 100% interest in the three Cecilia-Margarita concessions by making the following cash payments and share issuances:
  • the payment to the Optionor of a non-refundable deposit of $10,000 concurrent with the execution of the Letter Agreement;
  • the payment to the Optionor of $15,000 and the issuance to the Optionor of 100,000 common shares of Riverside concurrent with the execution of the Mexican Agreement* (the “Effective Date”);
  • the payment to the Optionor of $25,000 and the issuance to the Optionor of 200,000 common shares of Riverside on or before the first anniversary of the Effective Date;
  • the payment to the Optionor of $75,000 and the issuance to the Optionor of 300,000 common shares of Riverside on or before the second anniversary of the Effective Date;
  • the payment to the Optionor of $125,000 and the issuance to the Optionor of 400,000 common shares of Riverside on or before the third anniversary of the Effective Date.
The Cecilia-Margarita concessions are subject to a 1% NSR royalty in favour of the Servicio Geologico Mexicano (formerly Consejo de Recursos Minerales).
During 2017, Riverside completed a work program of rock-chip sampling that was designed to primarily confirm the existence of the more intensely mineralized gold occurrences found on Cerro Magallanes.  The sampling work was done within an area of roughly 1 kilometer by 200 meters at the core of the project area and mainly on the eastern and northeastern slopes of Cerro Magallanes. 


The Cecilia project is centered on a large middle Tertiary age (Oligocene) rhyolite flow-dome complex that forms the prominent topographic feature of Cerro Magallanes.  The dome complex intrudes and unconformably overlies a sequence of marine clastic sedimentary rocks consisting of interbedded siltstone and fine-grained sandstone and thin layers of intraformational, immature pebble conglomerate (middle Cretaceous Cabullona Group). The upper portion of the flow-dome complex is composed of a mixture of finely or weakly quartz- and feldspar porphyritic massive, flow-brecciated and banded rhyolite.  The lower portion of the complex, as determined by drill-hole logs, is dominated by a thick unit of rhyolite lithic tuff and tuff-breccia and clastic sedimentary rock fragments supported by a tuffaceous, rhyolitic groundmass.  Irregular bodies of talus breccia exist as a litho-facies within the pyroclastic units. 
Gold mineralization is concentrated within an area of 1,000 meters extent in the east-west direction by 200 meters north-south, with the peak of Cerro Magallanes being at the western end of this zone. Multi-element geochemical data shows that gold is inconsistently associated with anomalous concentrations of Ag, Mo and Pb.  The correlation coefficient for the element pair Mo:Pb is 0.942, whereas the correlation coefficients for Au:Ag, Au:Mo and Au:Pb are only 0.274, 0.248 and 0.089, respectively.  Significant concentrations of silver occur at lower elevations in the flow-dome complex at the eastern limits of the 1,000 m by 200 m zone of mineralization that has been defined at Cecilia.

West Target Area

The main Cerro Magallanes peak and abundant workings occurs along a northwesterly trending ridge line that extends from the peak of Cerro Magallanes.  Riverside collected 45 rock-chip and gold is seen to be very finely disseminated in quartz-iron oxide (hematite-goethite) stringers and veinlets as well as in dikelets and irregularly shaped zones of brecciation in the flow-dome rocks along the ridge. The highest gold assay obtained was 2.69 g/t Au.  Trace elements showing slight enrichments in the auriferous samples are Mo, As and Sb.  
An underground working consisting of a 90m-long adit and three levels of small galleries for a total working length of 184 meters exists in the central part of the target area.  Identified as Obra 26, the working’s ‘galleries’ are aligned NW-SE, apparently following a mineralized structure with this orientation. Cambior’s sampling produced 32 chip-channel samples with gold ranging from 0.2 to 4.76 g/t Au, with 14 of these samples assaying greater than 1.3 g/t gold.  The working was developed in moderately to highly fractured rhyolite porphyry containing abundant disseminated and fracture-controlled hematite along with veinlets of quartz and fluorite.  Hematite appears to be partially derived from the oxidation of disseminated pyrite and no drilling has been done in the West target area, and is a high priority target for Riverside. 

North Breccia Target Area

The North Breccia target area is located on the northeastern slope of Cerro Magallanes, is evident as a prominent zone of iron oxide staining, and has demonstrated some of the most extensive gold mineralization found.  The target area has an outline of about 250 m by 100 m and is marked by multiple zones of hematite stained hydrothermal brecciation, locally, with open-space crystallization of colourless quartz and purplish-colourless fluorite. Quartz ± fluorite veinlets and stringers are also common.  Alteration consists of widespread disseminated and fracture-controlled hematite and hematite and clay-rich gouge material found in a number of mainly NW-SE trending minor faults.  Of the 21 rock-chip samples collected by Riverside, 18 samples returned gold assays ranging from 0.447 to 7.46 g/t Au.  Gold is the only trace element that is noticeably enriched in the mineralized rocks.  
CRM tested this prospect in 1983 with drill hole DDH-83-03 and appears to have passed through strongly fractured and faulted flow-dome lithologies that display structurally controlled silica and chlorite alteration.  The geological drill log shows it passed through variably silicified and chloritized porphyitic rhyolite for approximately 135 m, then chloritized and intensely fractured banded rhyolite for 30 m, and at a down-hole depth of 195 m it entered into rhyolite lithic tuff. Core samples were apparently collected for the entire length of the borehole but the assaying method that was performed on these samples was quite rudimentary, and as a result are unreliable.
Cambior tested this area in 1995 by four drill holes (138-95-08, 138-95-15, 138-95-18, 138-95-19). The best drill-hole intersection of gold mineralization was obtained in hole 138-95-08 that averaged 1.41 g/t Au over 30.0 m, starting 4.0 meters down the hole. Gold assay values for individual core samples, each being 3.0 m in length, ranged from 0.32 to 3.33 g/t Au. No other gold pathfinder elements were enriched in this zone. Drill-hole 138-95-19 appears to have passed through a portion of the same mineralized zone intersected by hole 139-95-08 and produced an 8-meter-long interval, starting 48 m down-hole, that averaged 0.653 g/t Au. 

Central Target Area

A linear series of pits and small underground workings extend from the peak of Cerro Magallanes eastwards down slope and define the Central target area. The westernmost occurrence of gold mineralization was sampled by Riverside at an elevation of about 2,170 m.a.s.l.  Two adjacent 1.5 m long chip-channel samples returned gold assays of 3.0 and 7.9 g/t Au, with another 2 m-long sample collected 5 m to the side assaying 9.0 g/t Au.  Samples were collected along a fault breccia containing crystalline quartz, which is suggested to be striking to east-northeast with a moderate dip to the south-east.  It is possible that the intersection of this structure with the 35-40° easterly inclined slope surface of Cerro Magallanes has resulted in the linear array of gold showings, tested by historical workings and several Cambior drill-holes.  
At an elevation of about 1,930 m.a.s.l. are the underground workings of Obra 16 consisting of an adit and small galleries on three levels, 5-10 meters apart, that together have a length of 438 m. Thirteen Cambior samples on the upper level of the working assayed between 0.5 and 7.4 g/t Au, with another 16 samples from the deepest level assaying from 0.5 to 2.6 g/t Au. Riverside chip-sampled up-slope from Obra 16 with 15 samples assayed between 0.5 and 3.38 g/t Au.  Further up-slope are the entrances to workings of Obra 19 and Obra 20.  Two boulders of coarse-grained, comb-textured quartz veining returned high-grade Au-Ag mineralization; samples 2466 and 2473 assayed 58.0 and 133.7 g/t Au, and 288.0 and 87.8 g/t Ag, respectively.  
The eastern end of the target area is marked by a 20 m by 12 m collapsed open-cut or ‘glory-hole’ that connects underground working Obra 13. Cambior’s sampling exposed finely quartz- and feldspar-porphyritic rhyolite hosting quartz-fluorite stringers, veinlets and patchy breccia matrices with 22 samples assayed between 0.5 and 4.2 g/t Au. Riverside collected 12 chip-channel samples that ranged from 0.2 to 3.31 g/t Au and 13.1 to 145.6 g/t silver. Greater concentrations of silver at this lower level is worth noting as it appears to be indicating the transition from gold-only mineralization found at higher elevations into a Au-Ag zone where Pb and Zn are also somewhat enriched (100’s of ppm’s).
The eastern half of the Central target area between Obra 16 and higher elevation workings of Obras 19 and 20 was tested by 5 drill-holes, 4 done by Cambior (138-09, -10, -13 and -17) and one drilled by CRM (DDH-83-4).  Results from the five drill-holes were generally weak, with the assays reported by CRM for hole DDH-83-04 considered to be unreliable.  Hole 139-95-17, drilled to the northwest at an angle of 45°, intersected a relatively broad zone of gold mineralization that started 30 m down-hole and continued to 72 m in the hole, averaging 0.49 g/t Au.  The maximum assay for this mineralized intercept was 3.26 g/t Au.
The eastern end of the target area, where the workings of Obra 13 and Obra 14 are found, was tested with another two Cambior drill-holes, 138-95-02 and 138-95-07, both of which returned no significant assays.

East Target Area

The East target area is represented by a north-easterly trending ridge at the lower eastern slope of Cerro Magallanes and is defined by clusters of anomalous gold.  At the southern end of the target area is the small underground working of Obra 10, while at the northern end, about 180 m NNE of Obra 10, are the workings of Obra 6 which occur at about 1,720 m.a.s.l., the lowest elevation of all the historical workings found at the project. Maximum gold assays for underground samples collected by CRM and Cambior were reported as 3.84 and 1.964 g/t Au, respectively.
Fifteen Riverside chip-channel samples assayed between 0.199 and 2.356 g/t Au. An additional sample of ‘dump’ material collected at the entrance of Obra 6 assayed 8.421 g/t Au and 207 g/t Ag while another sample of quartz vein ‘float’ assayed 13.9 g/t Au.
The East target area was poorly drill-tested by 3 drill holes, two drilled by Cambior and one by CRM.  Cambior’s hole 138-95-03 was drilled to the south-east directly beneath the working of Obra 10, while hole 138-95-06 was drilled from the other side of the ridge in a WNW direction, possibly stopping short of the inferred mineralized structure that was sampled on surface and in the old workings. Neither of the drill-holes intersected any appreciable gold. CRM drill-hole DDH-83-01 was collared about 70 m west of the Obra 6 working and was inclined to the south-east.  Core samples were collected intermittently down most of the length of hole, however the gold and silver values for these samples are considered to be unreliable.
The scientific and technical data contained in this news release pertaining to the Cecilia Project was reviewed and approved by Ron Burk, P. Eng., a non-independent qualified person to Riverside Resources, who is responsible for ensuring that the geologic information provided in this news release is accurate and who acts as a “qualified person” under National Instrument 43-101 Standards of Disclosure for Mineral Projects.



General Specs

Cecilia, Fronteras, Sonora

Commodities: Au-Ag
Deposit Type: Low Sulphidatio Epithermal Au-Ag Rhyolite Flow Dome Complex
State: Sonora
Municipality: Fronteras
Surface Area: 6,897.3075
Type Of Deal: Option
Go to Location: Lat: 31.0614 Lon: -109.8261
Kmz File:


Name: Douglas Coleman
Phone: +52-1 (662) 181-0189



Name Title No. Document
Cecilia Margarita Fraccion 1 223203
Cecilia Margarita Fracción 2 223204
Cecilia Margarita 223202
Violeta 239269



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