mine technician Christopher Wilson helps maintain
the Hazel-Atlas Mine.
Calif. — They call it a portal but, really, it’s more
like a gaping maw. The opening’s steel-enforced gates,
padlocked, take on an almost predatorlike aspect, a
gangster’s grill-work sneering back at you. A dozen of
us stood before this threshold, awaiting entrance, staring
at the concrete portico bearing the chiseled inscription,
"1930," and trying not to obsess over minute
cracks in the foundation.
guide for the morning, Mickey Rovere, sought to reassure
us — and by us, I mean just me and maybe that wary
8-year-old in the back — of the safety of the
Hazel-Atlas Mine, a long-dormant operation that extracted
first coal, then silica, from the foothills abutting Mount
Diablo. But, in the very act of assurance, in his repeated
furrowed-brow recitation of preventive measures and
liberal use of the phrase "structural
integrity," Rovere only heightened my anxiety.
have modern-day miners in here maintaining these mines
every day," Rovere said. "They are testing the
integrity of the rock to ensure that where we’re going
to be walking is going to be safe. But it is a state
requirement that we keep hard hats on. Remember, this is a
real mine. The hard hats should be a reminder that you are
definitely underground, OK?"
I have a thing — irrational, I know, but so be it —
about enclosed spaces. I fear depths, not heights, harbor
debilitating entombment fantasies, imagine all sorts of
worst-case, buried-alive scenarios, akin to what those 33
Chilean miners faced a few years back. Sure, the opening
of the shaft looked secure enough, inviolable even, as we
peered in while Rovere fumbled with the padlock and opened
the double-steel gates with an eerie creak. Structural
integrity, I told myself. Structural integrity. It became
a mantra, a lullaby to combat the decanted cortisol, that
toxic stress hormone, flooding my neural pathways.
one else appeared the slightest bit fazed, not even the
8-year-old. Their fascination with getting a glimpse of
history about a bygone energy-extracting industry, as well
as gawking at glittering sandstone rock 50 millions years
in the making and fossil remnants from what once was the
ocean floor, seemed to override any deep-seated angst.
After all, people have been touring the mine at Black
Diamond Mines Regional Preserve for two decades, not
counting that closure from 2007 to 2012 after storm damage
threatened the (wait for it …) structural integrity and
necessitated extensive repairs under rigorous mine-safety
inside, donning hard hats and clutching flashlights like
life preservers in the pleasant 57-degree coolness, we
prepared for a 90-minute trek 950 feet into the bowels of
Diablo’s foothills to observe the geology and learn how,
from the late 19th century to the late 1940s, miners
blasted into the rock to scrape away first coal and then,
when that rich vein ran dry, 1.8 million tons of silica
from the sandstone to ship to Oakland for making glass.
first, Rovere gave us the lay of the inland via a slide
show in a room chiseled out from the main shaft. In a
feverish 10-minute presentation, the peppy, fast-talking
Rovere took us from the early Cenozoic Era when Mount
Diablo was ocean floor and through tectonic upheaval and
formation of coal deposits. Then he segued into the
entrepreneurial forays in which 4 million tons of coal
were pounded out by workers, some just kids, for about $3
a day, while risking black lung disease, boiler explosions
and spontaneous combustion. Then came the sand-blasting
stope days of silica mining, where seven layers of
parallel tunnels snaked more than 7 miles, connected by
the time he got to the mine’s closure, Rovere, almost as
an aside, told us "the reason we became a park,"
which did nothing to quell my anxiety.
mines produce gases — methane, carbon monoxide, carbon
dioxide — and, after the mines closed, a lot of young
explorers wandered into them and couldn’t find their way
out. These gases were overwhelming. So … (the East Bay
Regional Parks District) came in for public safety, sealed
off all of these coal mines, using special foam and
concrete and opened this one making sure the structural
integrity was sound.
I like to call this is an 89-year-old sand castle …
except we don’t have a tide that comes in and washes us
away. We have state-certified miners who come in and
gently tap on these walls and ceilings — we call it
scaling — all week long to test the structural
integrity. OK, any questions?"
always one in every group, some dolt who holds everyone
back from actual exploring with an alarmist question. That
person happened to be me. I asked about earthquakes.
actually going to walk right through a fault," Rovere
said. "In 1989 (the Loma Prieta quake), we had just
one rock fall."
that’s nothing," I said, relieved.
was a 700-pound rock, so it wasn’t nothing," he
said. "It came out like a loose tooth right over
pointed to a spot near the portal, saying, "It
crushed all our (equipment). That’s why this area is all
reinforced concrete, to protect walls."
as we trudged ahead about 30 feet through the tunnel,
about 8 feet high and 10 feet wide, the concrete and wood
reinforcements ended. We were surrounded by sandstone. I
brushed my shoulder against a pillar and sand crumbled
down my arm. Such porousness didn’t inspire confidence
in, well, the structural integrity of the walls.
stopped us at a re-creation of a Brass Board, where miners
would punch in and the boss could see where in the bowels
of the pit they were toiling.
boss is responsible for my life as a miner," Rovere
said. "As I mentioned, lots of accidents happen. We’re
using dynamite. We’re blowing up rocks.
our job. Rocks fall – on purpose. They hurt, too. OK,
let’s move on."
the next 30 minutes, Rovere showed us all aspect of
sand-mining operations: the cavernous stopes where miners
toiled; chutes where rock traveled on its downward tumble
to the rail carts; ominous-looking machines called muckers
made to clear the rubble with a catapultlike lever; pipes
used to carry water to keep the dust down after blasts;
holes left by 6-foot drill bits from pneumatic augers;
holes left by "prehistoric burrowing ghost
shrimp" in walls that formerly were the ocean floor;
the office where the pit boss kept an eye on the number of
carts chugging by.
job here was simple," said Rovere, who had sort of
internalized the experience and deputized us as fellow
miners, a tad unsettling for a guy who’s only had desk
jobs. "We had to haul out as much … earth as we
possibly could without letting the hillside collapse. We
had to leave behind these large structural pillars to keep
the integrity of the hillside."
shuffled on, following the rail tracks deeper in, the
space lit by bare bulbs. Rovere had us shine our
flashlights on a large bulge of white silica sandstone,
"95 percent pure silica oxide," and the light
reflected back at us, delighting the 8-year-old in the
thought it was pretty cool, too, and felt my anxiety quell
that silica oxide is melted down with soda ash and
limestone," Rovere explained, "you’ve got the
clearest glass available in that era – Depression glass,
1924 to ‘46. Made a lot of Mason jars for California
BEGIN OPTIONAL TRIM)
when Rovere led us to an archway, whose stone was a darker
shade of brown, veined with white, his voice fell to a
he said, "is that ancient fault line I talked about.
The Hazel-Atlas Fault. You are underground looking at the
actual fault. This is a slip fault. The side of the hill
you’re standing on snapped and slid down, changing the
type of rock to epsonite, which you couldn’t mine for
glass. Geologists came in and found where the white silica
had gone to. See how the rail tracks curve right here?
They had to change direction to keep mining, the
earthquake fault displaced it that much. Don’t worry,
this is really solid rock."
900 feet in, almost to the end — or, more accurate to
say, the end of the part of the tunnel that East Bay
Regional Park District workers deem safe to traverse —
Rovere had us stop and peer down over a bridge to utter
blackness hundreds of feet below. We shined our
flashlights into the chasm and could make out a few jagged
at the second level, looking down at the first
level," he said. "There are seven floors of
mines here, one on top of the other."
we reached the end, but before we turned back to retrace
out steps, Rovere instructed us to tilt our heads upward
and take in the sandstone ceiling, pockmarked with square
of these (sandstone) pillars left behind by the miners as
broken bones in need of surgical pins," he said.
"Each one of these pillars holds back 300,000 tons of
pressure in the hillside above our heads right now.
got the feeling Rovere had sensed my fear — or maybe saw
me excreting sweat from every pore — and was just being
overly dramatic to goad me into shaking like a chihuahua.
so there’s 600 feet of solid rock above us," he
continued. "That’s why you’re wearing the
picked up my pace on the way back to glorious daylight,
pausing only to look at a sign near the portal stating,
"Safety Is Your Responsibility." Later, as often
is the case with me, I felt a bit ridiculous for being so
jumpy. I was never in any danger, the hard hat and the
verbal warnings merely part of the entertaining tour,
days later, when I returned to the office to write this
story, I googled the mine, and this headline from The
Contra Costa Times, dated June 9, 2015, popped up:
"Worker injured by falling boulder at Black Diamond
Black Diamond Mines Regional Preserve, 5175 Somersville
Visitors center open 10 a.m. to 4:30 p.m. on weekends from
March through November; mine tours require reservations;
call (510) 544-2750
Tours are $5; parking is $5
information: ebparks.org/parks/black — diamond