Friday, March 22, 2013

Answer: What came from the mine?

Sorry about taking an extra day to give you the answer.  These days are busy, and sometimes things get slightly out of hand. 
The real reason... I’m busy reshooting videos for the refresh of our “Power Searching with Google” MOOC (online class).  If you missed it on the earlier passes, there will be another chance for you to take it beginning around mid-April.  Stay tuned—I’ll be sure to let you know exactly when it is.  (But in the meantime, that’s what’s consuming all of my time these days.)
On to our search challenge…  

Recall that the questions were (1) When did the mine open?  And, (2) What was mined here?

First, you have to realize that the GPS data wasn’t quite right.  Once you’ve extracted the lat/long from the EXIF data, you’ll quickly see that there’s no labyrinth exactly at that location.  The quarry hole and labyrinth are actually at: 37.853058, -122.190440 (I assume you figured that out and just panned around the location in Maps for a minute before finding the actual location).  

By looking at the map I could easily tell that this location is part of the Sibley Volcanic Regional Preserve, which is a beautiful open-space preserve run by East Bay Regional Park District.  

So I started with the obvious query: 

[ Sibley Volcanic Regional Park history ]

I then did:

[ "round top" intext:quarry sibley ]

and found an article in BayNature (a local natural history magazine) that mentions the quarry was “Kaiser Sand and Gravel.”    (I later watched a video that was posted on the Sibley Parks page where naturalist Steve Edwards says the same thing.  See: )

Now we have our first clue:  The quarry was the “Kaiser Sand and Gravel” company. 

I know that counties often track industrial sites and mines are often described (for historical reasons) as being in a particular county.  So after looking at my map to see what county the Sibley Preserve was in (A: Contra Costa) my next query was: 

[ Kaiser quarry Contra Costa ]

Which led me to a remarkable map at  (a site that compiles information about mines—who knew there would be such a resource!) 

A quick look at the map, however, tells me there are TWO mines/quarries in that immediate vincinity.  The “Henry J Kaiser Company Mine” (aka “Kaiser Sand and Gravel) AND the “Tunnel Rock” mine.  Let's check out these alternate lead.  

A search for: 

 [ “Tunnel Rock” mine Contra Costa ] 

leads me to, which gives me the lat/log (37.855202, -122.201851) for the Tunnel Rock min and a description of what they mined (“construction sand and gravel; broken stone”) 

Well… THAT’s interesting!  Is it really the same mine by two different names?  Doing the same thing for: 

 [ “Kaiser * mine”  Contra Costa gravel ]

show a few additional results.  (Since there are SO many Kaiser mines, I had to add in “gravel” to limit my search to something managable).

Looking at the content, I see much of the data comes from the book: "Mines and mineral resources of Contra Costa County"  (1958) – alas, it’s not available on the web.  (I discover later that this book is an extract from “California Journal of Mines and Geology, volume 47 (1951)”… also not available on the web.) 

BUT I can find a copy in the library!   (And I’ll head over to Stanford later this week to see if I can find it in the stacks.) 

I still haven’t figured out if this is a different mine, or the same mine.  Searching for 

[ “henry j Kaiser company mine” ]

(a variant phrase I picked up from reading), I find another resource that gives me the lat/long for this mine:  37°51'36", -122°12'1"

Continuing my search, I find another good hit at that repeats what we saw earlier—that the quarry was used for broken rock, sand, and gravel. 

So… after much looking around, I discover that there are actually TWO mines near that location.  There’s a great page on that shows the distance between the mines:  (shows that Tunnel Rock and Henry J Kaiser Company mines are within 1700 feet of each other).   Their map shows it like this:

And the Kaiser mine: 

Here’s my Google Maps version of the two mines.

The Kaiser mine is the red arrow, and the Tunnel Rock mine is in blue.  

So now… when did they open? 

Like other readers, I’ve only been able to find a few clues here and there.   I found a couple of hiking guide books that claim the mines were opened in the 1930s… but they don’t say where THEY found that information, so I’m worried that the reliability might not be very high. 

And when I look at this location with Google Earth (using the Time Slider), I see the following images—from 1939, 1993, and 2002.

So… I’m a little stuck here.  I think we’ll have to find an additional source of information.  Were these mines REALLY active between sometime between 1993 and 2002?  OR… is the Google Earth image for 1993 just mislabeled??  

More research is required!  Ideally, we'd like to find a different aerial archive image with dates in the 1930s and '40s; or maybe someone's first-person account of mining in this area.  

The labyrinth: By the way, the labyrinth is the work of Helena Mazzariello:  see her page on the labyrinths at

Result:  Still searching!  


  1. Hi Dr. Russell.

    Searching found some data. I will search more.

    ["Kaiser Sand and Gravel" basalt quarry california Round top] to find:,2732370. It says Kaiser sold the quarry in 1977 to the park district.

    ["Tunnel rock quarry" california closing]
    Here it says ThatKaiser Quarry opened 1954. I believe is another quarry because it doesn´t tell us more. It also mentions Tunnel Rock in the same year.

    Have a great weekend.

  2. Querying the quarry, mine is mine?

    Searched for ["tunnel rock"] (a resource I found yday after long searching) and reached the following info:

    Mineral Information Service August 1, 1956


    Rock products continue to be the leading mineral
    commodity produced in Contra Costa County. Five
    crushed rock plants are qperating, of which three
    are comparatively new. These are the Kaiser and
    Pacific Coast Aggregate quarries located close to
    one another near Clayton,and the Tunnel Rock quarry located near the east end of the Broadway tunnel.

    The Kaiser quarry is a relatively new operation
    while Pacific Coast Aggregates took over the old
    Harrison-Birdwell quarry. Both quarries have been
    operating since January 1954 producing unwashed aggregate from black igneous rocks of the Franciscan formation (Jurassic ?). The aggregate is used predominantly for road base. Each plant has a capacity of 250 tons of crushed rock per hour .

    For the past few years crushed rock has been
    produced from the volcanic rocks of the Moraga for mation (Pliocene) at the Tunnel Rock quarry in the hills southeast of the Broadway tunnel. Unwashed volcanic rock is crushed for road base at an estimated rate of 100 tons an hour . Some large boulders are also quarried for riprap."

    So it seems the quarry opened in the 50s.

    1. Excellent find. Can you say how you found

    2. Yes, I searched for ["kaiser sand" 1977] or something similar on and found some interesting pdf. The address looked yummy so I went through the dirs of the domain and saved it for later research.

    3. checked out the link provided by maca that references a Kaiser quarry and an RCM operation of the former Harrison-Birdwell quarry that are "near" each other and the "Tunnel Rock quarry located near the east end of the Broadway tunnel."This site actually appears to be in SF, south of Russian Hill - the location of the Broadway Tunnel.
      Looking at these 3 locations seemed to indicate they were all out of the area (Sibley) in question. The Kaiser site mentioned, as well as the H-B site were south-east of Concord, on the east & south end side of Mt. Diablo State Park.
      Clayton/Concord area
      H-B Clayton quarry site
      Broadway Tunnel location
      Broadway Tunnel
      part of the problem seems to be the large number of quarry operations that have existed and continue to operate to this day, under companies that have had their ownership/names changed repeatedly.
      Thought you might be interested to see that the Caldecott Tunnel expansion continues present day. Also included a link to the quarry outside Cupertino because it contains some history and illustrates the point.
      Caldecott 4th bore
      Caldecott history
      Cupertino quarry(Kaiser)
      This is starting to raise the question of the value of information - what's worth finding and when....

  3. I know this falls in the speculative realm, but a couple of things seem plausible - given the visual state of the quarry area and Sibley's history (renamed after Sibley following his death in 1958, previously Round Top Regional Park, one of the first three parks of the East Bay Regional Parks District -1936. It would seem reasonable from a liability standpoint that private enterprise mining operations wouldn't be occurring in areas open to the general public.
    It would also seem likely that a large percentage of the product produced out of the two quarries was used in the Caldecott Tunnel project - indeed, as you discovered, one of the quarries was named "Tunnel Rock Mine". The Caldecott project started the first two bores in 1929 and completed that phase in 1937 and that time frame would/could roughly correspond with the quarries in question being in operation. Not definitive, but seems reasonable.

    Also am curios where the early aerials come from for the Google Maps views 1938 would note there seems to be a lack of machinery in those images.

    quarry conditions
    Round Top Regional Park

    1. You know, that's what I was thinking too. The Caldecott tunnel is a big project nearby that was going on at about the same time. But I can't prove it... yet.

  4. I believe you can see the mine in the 1993 photo, it is just so much lower quality that it is hard to see. There is a white area on the right side of the mine visible as well as the cliff to the left(southwest) of the pit.

    1. I'm still looking for better images of the area in that time.

  5. Dan, would you mind quickly elaborating on why you decided to use the "intext" operator in this query of yours:

    [ "round top" intext:quarry sibley ]


    1. Sure... There are LOTS of things called "round top" in the world. And there are even a fair number of pages with "Round top" and Sibley in them, as that's the name of a mountain ("Round Top") in the Sibley park. But if I require that the word "quarry" be on the page, then that will give me ONLY pages that have the word "quarry" on them. In other words, it really reduces the number of false positives (that is, pages that look good, but don't actually have anything on them about quarries).

      I also experimented with [ "round top" intext:quarry OR intext:mine OR intext:mining sibley ] -- but it turned out to be overkill. Didn't need to go that far.

  6. Okay totally off topic but actually is interesting. It appears to be FBI files on the Zodiac Murder and Robert Sibley Volcano Preserve is mentioned if you want a break. I will let you guys argue out your findings on the mines and quarries of the area. We seem to be spreading out the possibilities rather than focusing closer which allows for more vague leads. But I hope Dr. Dan is able to find firm evidence at the university. fbi zodiac murder

  7. My 5 cents:
    Searched on [Caldecott tunnel quarry kaiser sibley]
    Sibley Volcanic Regional Preserve, in the Oakland hills. View north. The two peaks in the distance are Grizzly Peak (l) and Vollmer Peak (r). The foreground has equipment pads related to the Kaiser lava-rock quarry that was here for about 75 years. The basalt beds hold up the ridge on the right and are extensively quarried, revealing deep cross sections of a small volcano that existed here about 10 million years ago. Since that time the volcano and the sedimentary rocks beneath it have been folded and tilted eastward. You can see the layering of the sedimentary rocks in the nearmost ridge. Conglomerate rock has less soil and dries out brown, while the shales retain water better and support thicker growth. You can see the rocks are now tilted almost vertically. State route 24 runs behind the ridge in the middle distance, entering the Caldecott Tunnel under the ridge just off to the left.

    Photo taken in 2005; quarry that was here for about 75 years => quarry opened in the 1930s (but no "scientific" proof).

    Unfortunately no lat/long coordinates from the EXIF data.

  8. Here’s a recap of the Caldecott Tunnel Construction

    And here’s an article that connects Kaiser to the Caldecott Tunnel contract.

    “As we all know, the Broadway site won out, and in 1934 $2.8 million in bonds were sold, $1 million in federal money was secured and a $3.7 million bid by Six Companies of California, the consortium that built Hoover Dam, was selected by Joint Highway District 13, the local agency formed to build the tunnel.”

    Note in the above the mention of the Six Companies Group(which I know from earlier research was actually 8 companies) and Henry Kaiser was the lead negotiator for this group. From the research we may be assuming Kaiser Sand and Gravel owned the quarry in question, but I think it’s possible that it was one of the other 7 companies in this group of companies. It may have just been recorded in history inaccurately.
    That’s all I found and perhaps it will help complete the search.

  9. Just when I thought I was done..

    One more tidbit

    “Construction of the Broadway Low Level Tunnel began in 1934. However, the contractor, the Six-Man Company, was unable to complete the construction stages in a timely manner. With 68 percent of the project complete, the contract was broken down into smaller contracts and awarded to individual companies to complete the project.”

    1. This comment has been removed by the author.

  10. a visual metaphor for this quarry query - found as I was gnashing my teeth on small pebbles of basalt in an almost infinite Google search results labyrinth - dark>light>speed>more darkness>404 message>stop>marine layer... I needed SRS diversion/healing...
    Caldecott vision

    “Most human beings have an almost infinite capacity for taking things for granted. That men do not learn very much from the lessons of history is the most important of all the lessons of history.”
    ― Aldous Huxley

    I love the smell of Basalt in the morning.
    — the ghost of Hunter Stockton Thompson
    fishy Basalt

    oh, to be a Google Goat and be free of such endeavors... Baaaa.
    serp goat

  11. ["Henry John Kaiser" AROUND(3) Round top quarry]
    To find:

    CTRl-F (quarry) to find 1923 was the beginning of Kaiser Sand and Gravel Company.

    Have a great sunday.

  12. Under the adagio “if you don’t know the answer, try to find someone else who knows” I contacted the several times mentioned Dr. Stephen W. Edwards ( Botanic Garden Director, Regional Parks Botanic Garden, Berkeley) who mapped the geology of these hills in 1982. Dr. Edwards was several times trip leader in geological field trips:

    This morning I got his answer: “Sorry, I have not involved myself with the history, only the geology”.

    Alas; we have to dig further.

  13. Just checking in to see how others have done. I startedvto wonder what road materials would havebeen use in the tunnel construction. In addition to below I found basalt was used in paving blocks which I believe was used in the tunnelcin 1930's. Not much to add but following excerpts...

    Query[history basalt california]
    "By 1913 approximately 74 quarries were in operation in the San Francisco Bay area. Of these, 43 percent produced paving blocks; 30 percent, building blocks; 25 percent, crushed stone used for concrete and road metal; and 2 percent, abrasives including ground pumicite."
    "(Circa 1950)California has the largest commercial output of rock products of any of the 48 states. It is far ahead of any other state in production of sand and gravel, and ranks near the top in production of crushed and broken stone. Of the total rock products produced in the state about one-third comes from the San Francisco Bay counties"

  14. Hello Dr. Russell, Rosemary and fellow Searchers!!

    ["Henry John Kaiser" AROUND(3) Round top quarry]
    To find:

    There used CTRl-F "quarry" to find Henry John Kaiser biography. 1923:Started Sand and gravel quarry at Radum (near Livermore), to supply the Livermore-Pleasanton paving job. This was the beginning of Kaiser Sand and Gravel Company.

    I wrote to "Sibley Volcanic Regional Preserve" and thet sent a document in which they bought abandonded quarry in 1977.

    All the best

    PS. Rosemary, I just read your message from the books post. I'd like to learn more with you and maybe work together in thex challenges if you want. Do you have G+? How can I contact you. Have a great week

    1. Nice, really interesting find. This does show that Kaiser S&G started in 1923, but that's a big organization and not necessarily the time of the start of the Round Top quarry.