This is perhaps the best time of year to visit Vasco Caves Regional Preserve south of Brentwood.

Accessible only by guided tours, the preserve has spectacular rock outcrops, vernal pools with rare and endangered fairy shrimp, and pictographs created centuries ago by Native Americans. The preserve also is habitat for eagles and other raptors that hunt ground squirrels in the grasslands.

Tours last from 9 a.m. to 2 p.m. They leave from Round Valley Regional Preserve near Brentwood or Brushy Peak near Livermore, aboard buses provided by the East Bay Regional Park District.

As of this writing, there are openings on tours scheduled for March 30, and April 6, 13 and 19. The cost is $30 per person, $34 for nondistrict residents. For up-to-date information and reservations, call 888-327-2757 and select option 2.

BLACK DIAMOND: After the usual winter break, the underground mining museum and visitor center at Black Diamond Mines Regional Preserve in Antioch have reopened for the 2014 season.

Tours of the park's Hazel-Atlas silica sand mine are available by reservation at 11 a.m. and 2 p.m. on Saturdays and Sundays. Groups of 10 to 15 people can reserve a 10 a.m. tour. First-come, first-served tours are at noon and 3 p.m.

Tours last about 90 minutes, taking you through 1,000 feet of a restored silica sand mine that was active from the 1920s through 1940s. Mining equipment is on display, and guides explain the techniques by which silica was extracted for use in foundries and glassware production.


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Tours cost $5 per person. For safety reasons, children must be 7 years or older to participate. For information and reservations, call 888-327-2757 and select option 2.

All ages are welcome free of charge at the park's underground Greathouse Visitor Center, which features artifacts and photos from the 19th-century coal mining era. Visitor center hours are 10 a.m. to 4:30 p.m. on Saturdays and Sundays.

As long as we're at Black Diamond Mines, there are a couple of interesting programs scheduled there this coming weekend.

Naturalist Bob Kanagaki will lead a walk through the site of Somersville, a now vanished 19th century mining town. Designed for ages seven and up, Kanagaki's program is from 10 to 11:30 a.m. on Saturday.

Then from 10 a.m. to noon on Sunday, naturalist Eddie Willis will lead a hike to Rose Hill Cemetery, final resting place for many of the miners and their families who lived and worked in the area. It's for ages 6 and older.

Both hikes are free of charge and reservations aren't required. Both start at the parking lot at the upper end of Somersville Road, five miles south of Highway 4 in Antioch. Rain cancels both hikes. Black Diamond Mines has a parking fee of $5 per vehicle when the kiosk is attended.

Rain or shine, some early spring wildflowers are starting to appear at Black Diamond Mines. Among the first is Indian warrior, a maroon flower with feathery leaves that looks a bit like a bandsman's pompon. You can see it under the manzanita bushes on the Ridge Trail and Chaparral Loop Trail. Indian warrior is a "hemiparasite," which means that it can live on its own, or draw nourishment from the manzanita roots.

love them snakes: A reptile rendezvous is on the calendar for 2 to 3 p.m. Saturday at Tilden Nature Area in Berkeley. It's a chance to meet and greet the nature area's reptiles-in-residence, learn some reptile lore and make a craft item to take home. Your human host is interpretive student aide Tricia Radis.

There's a large stand of eucalyptus trees in the nature area. In a program from 2 to 3:30 p.m. on Sunday, you can learn the history behind the trees, then make and decorate your own walking stick out of a eucalyptus sapling, assisted by interpretive student aide Sam Fuller. Materials and tools will be provided.

Both programs are free. Both will be at the Environmental Education Center. Because of ongoing construction, you have to access the center by parking at the end of Lone Oak Road off Tilden's Central Park Drive, then following the signs on foot to the center. For information, call 510-544-2233.

Ned MacKay writes a regular column about East Bay Regional Park District sites and activities. Email him at nedmackay@comcast.net.