My friend Nick and I hiked to Newberry Cave in mid-March, 2011. This cave is on the edge of the Newberry Mountains Wilderness east of Barstow. This area is not well-traveled and you probably won't find concise directions to the cave on the internet, and I won't divulge them here. But armed with a little bit of research and studying of Google Earth maps, and then with some cross-country hiking and rock scrambling, you, too, may be able to find it.
The cave doesn't appear to be a traditional limestone formation, but rather the rock here is very loose and brittle and it appears that it was created when a large portion of the cliff collapsed. There are no stalactites or stalagmites or any other traditional cave formations inside. The cave walls are black from ancient campfires, and packrats currently call it home.
This cave was the site of some exciting Native American discoveries - there are some faint white, red, green, and black pictographs near the entrance that are unique and do not match any known forms previously found in California. And archaeologists have found artifacts dating back to 6,000 years ago inside. The San Bernardino Museum Association excavated the cave in 1953. They found the bones of an extinct Shasta ground sloth, over 1,000 fragments of atlatl shafts, 78 projectile points, split elderberry twig figurines, pigment stones, sandals, cordage, fire drill sets, stone and bone tools and quartz crystals.
Outside, if you visit in the springtime, you may find some fantastic wildflowers blooming including carpets of desert gold, desert dandelions, phacelia, heliotrope, ghost flowers, and one of my favorite flowers, desert five spot. There are also plenty of opportunities to spot desert wildlife in this area - lizards, snakes, birds, squirrels, even bighorn sheep if you are lucky enough.
Be careful as you are hiking in this area as all the rocks are very loose and can become dislodged from underneath you with the slightest movement.
If you find the cave, please respect it. Leave any artifacts you may find and make sure others in your group do so as well. Please practice Leave No Trace ethics. Remember that the desert is very fragile, and scars take a lifetime or more to heal.