2:PC&N Sonoma Magnesite Mining Scene

Prototype Research

The Sonoma Magnesite Company operated a Magnesite mine along Austin Creek north of Cazadero that interchanged with the narrow gauge.  The mine operated a 2′ narrow gauge tramway from its claim on one end to the Cazadero area.

The mine operated intermittently from roughly 1914 to 1925.  The need for the mine and others like it was due to the US being cut off from its primary source of Magnesite, Austria, during World War I.  This mine produced poorer quality ore and incurred high transportation costs in interchanging their 2′ tram with the narrow gauge then retransferring their loads to standard gauge.

Yet as you will see, this is a very interesting mining operation to model.  The technology used, engines, cars, structures, and equipment fit in nicely with a turn of the century prototype.

This is a current Google map of route of tramway north of Cazadero.


The upper camp was called Magnesite, the middle camp Mannings Flats and the bottom camp, Baldwins.  Bottom symbol was the interchange with the narrow gauge in Watson Station, about two miles south of Cazadero.  Today this route is a road, Cazadero Highway.

The map of the claim itself shows a significant number of plots spread out along Austin Creek.  This terrain was rough and required a significant number of trestles and sharp curves.  The tramway ran through the mining district to the plant, then down Austin Creek to Watsons, two miles south of Cazadero.


These three images are from “Narrow Gauge to the Redwoods”.  They show a tram consist.  The flats carry bags of refined magnesite ore.  Magnesite ore was also shipped in paper lined barrels .


In this shot, “Betsy”, a Davenport 0-4-0 Dinky is on point.


This shot is a bit earlier in the mine’s history and shows, “The Hippo”, a distillate locomotive.


This shot of the Dinky courtesy of the USGS.


These shots are from the California State Mining Bureau Bulletin.  This shot shows a Magnesite deposit in the Sonoma claims.  Note the man standing in the photo.

Magnesite Deposit

This is the rotary kiln used by the Sonoma Magnesite Company to refine the ore.

Rotary Kiln

This is the ore chute used to get ore from the upper to the lower claim.


Here’s a shot at the bottom of the chute.


This shot is at the top of the chute.


Another mine entrance – Cecilia claim – Sonoma Magnesite.


This is the ore processing mill containing the 50 foot rotary kiln.  This shot is most likely to be taken just after the shed on the front of the structure was added in preparation for installation of a second rotary kiln.  That the kiln is not yet installed is obvious in that a second stack is not yet present on the right side of the roof line.


The following are typical mine shots, not from the Sonoma Mine.

This is a rotary kiln at the Sierra Magnesite Company.  Note the size of the man relative to the kiln.  This photo was used to take off dimension estimates for the Sonoma kiln.


Mill house containing rotary kiln.  Note the timber structures on each end of the building  It is likely a rough crusher was located under the structures on one end and a fine crusher on the other.


This is a typical tram way.  Gondolas contain ore that hasn’t been processed.


Typical ore dump.



A major section of the railroad is set aside to model the Sonoma Magnesite tramway including the mines and the plant.  No track plan exists other than the plot map shown above.  While this tramway was a 2′ narrow gauge, I have chosen to model it in HOn30 (2 1/2 feet) due to improved availability of engines, rolling stock, and track.


The main structure modeled will be the mining operation containing a single rotary kiln.  The kiln will be oil fired both from the standpoint of heat and to fire a boiler and steam engine that will drive the equipment.  I plan to model with the front shed shown in the prototype photos.  The front wall will either be open or removable so the equipment inside the mill can be viewed.  Ore will come into the plant in mining cars and the processed ore will leave on flat cars or in drums.  The plant will be scratch built.

The crusher will be kit bashed from the Campbell Ore bin.

Campbell Ore Bin

In addition a number of smaller mine structures will be modeled (TBD) as well as the ore chute shown in one of the earlier photos.  There will be extensive trestle work in this area.


Track will be HOn30 or N scale.  A number of options exist including Peco HOn30.


A  single small steam switcher will be assigned to this area.   The search for a suitable switcher is active, but a Davenport 0-4-0 saddle tanker would be ideal closely matching the prototype.

Rolling Stock

Rolling stock will be scratch built or kit bashed.  Consists will include:

  • Small flat cars (to carry processed ore and drums.
  • Oil tank cars (providing oil for the kiln.
  • Low gondolas (to carry raw ore)


Because of the gauge difference an interchange will be built in Watson Station.  A transfer dock will be built allowing ore to be transferred from flats to PCN boxcars.  Oil transfer will all need to occur at this location.

Here is a listing to posts that cover implementation of this section of the layout.

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