Entry No. 39 — the Santa Barbara file — filed under: mine
Coquina Mine
Located in the Marr Ranch Open Space of Simi Valley, the Coquina Mine is an abandoned 1930s limestone quarry once operated by the Tapo Alto Shell & Fertilizer Company. Active from 1929 to 1935, the site was mined for fossil-rich limestone to produce calcium carbonate. Today, hikers can find rusted relics left behind, including a vintage P&H Model 206 power shovel and other decaying machinery.
The story
High up in the foothills of the Santa Susana Mountains inside Marr Ranch Open Space, you are standing on the remnants of an ancient seabed that was briefly mined for commercial fertilizer. From 1929 to 1935, the Tapo Alto Shell & Fertilizer Company set up shop here to quarry fossil-dense coquina limestone. Their goal was straightforward: grind down prehistoric shell deposits to extract calcium carbonate for agricultural soil conditioning and livestock feed.
When operations ceased in 1935, the company skipped the cleanup entirely. They walked off the site and left their heavy iron infrastructure to crumble in the dirt. Today, the centerpiece sitting stranded in the scrub is a vintage P&H Model 206 power shovel—a hulking 1920s excavator frozen mid-shift alongside scattered gears, iron bits, and quarry cutouts.
What it's like
The trail through Marr Ranch Open Space is open and exposed, so pack extra water and prepare for direct sun. Once you hit the quarry site, you will find the power shovel standing right near the path. Keep your hands to yourself and stay on the official trail—the ironwork is jagged, unstable, and rapidly degrading after nearly a century of weather.
The move: Hike the scenic Coquina Mine Trail together, enjoying views of the Santa Susana Mountains while photographing the historic, rusted mining equipment from a safe distance.
📍 Before you go The mine is located along a public hiking trail in the Marr Ranch Open Space, but visitors should remain on the trail and only view the unstable, rusted machinery and quarry site from a safe distance.
- 📍 Coquina Mine
- 💸 Free
- ⚡ Low-key
- 🌗 Outdoors
Where: Coquina Mine, California 93063, USA
Hours: Added 2026-07-20 — confirm current access before you go.
Pair it with
- Beatrice Wood Center for the Arts — Pair an industrial rust hike through Simi Valley's back hills with Beatrice Wood's Dadaist ceramics studio up in Upper Ojai.
- Montecito Hot Springs — Trade the dry, iron-heavy quarry ruins of Marr Ranch for the lush, stone-walled hot springs ruins winding through Montecito.
- Ganna Walska Lotusland — Follow up abandoned 1930s heavy machinery with the eccentric, hyper-curated botanical theater of Madame Walska's estate.
Good to know
What was mined at the Coquina Mine?
The Tapo Alto Shell & Fertilizer Company extracted fossil-rich coquina limestone between 1929 and 1935 to produce calcium carbonate.
What key relics remain at the site?
The main attraction is a vintage P&H Model 206 power shovel, alongside decaying iron equipment and quarry remnants.
Can you climb on or enter the old machinery?
No. The rusted machinery and quarry cuts are unstable. Visitors must remain on the public hiking trail and view the equipment from a safe distance.
Where is the mine located?
It sits along public hiking trails in the Marr Ranch Open Space in Simi Valley.
Plan a visit & invite your people →
Further reading: visitsimivalley.com · photographyontherun.com · alltrails.com
last checked: 2026-07-20