2. Morro Bay, CA Volcanic Igneous Dacite I took a trip to Morro Bay because I thought that it would be a great place to search for rocks! First thing that you see when you pull into the beach is the massive mountainesque rock called “Morro Rock.” I saw that there was a pile of rocks at the base of Morro Rock that seemed to have fallen off recently so I picked up one as one of my samples. Morro Rock was formed about 23 million years ago from volcanic plugs so my rock should date to sometime around then too. In researching my Morro Rock I found that it is mostly made up of volcanic igneous dacite, and that would be my best guess for this rock. It appears to me to have bits of quarts in it that are very noticeable but there are also some flecks of black in it which may be horneblende although I am not too sure about that.
3. Morro Bay Continued…. Sedimentary Sandstone Walking along the beach of Morro Bay I came across this rock. I believe that it is sedimentary sandstone because it is very fine and the particle shape seems to be very well sorted. It was formed from pressures and compaction of sand grains over the span of millions of years. It has small “potholes” in it and a distinct smooth surface which was probably the result of being washed over by the waves and rubbed the course grained beaches. My best guess is that this rock started forming over 20 million years ago and the eventually ended up this way after years of erosion and pressures.
4. Morro Bay Continued…. Metamorphic Schist This is another rock that I found while walking on the beach. The thing that I like about rock hunting on the beach is that you can find all kinds of different rocks from all over because they could have been carried by the waves of the ocean. I believe this rock to be Metamorphic Schist. From the look of it I believe that it is mostly made up of a blackish mica with what looks like quartz intertwined. This rock was probably made from heat and pressure folding the original sediments together some twenty million years or so ago. The pressures made this rock what it is today, a folded layer upon layer of different colors and textures.
5. Columbia, CA Pyrite (Fool’s Gold) I took my daughter and my sister up to Columbia, CA which was a booming mining town after gold was found in 1849. Now it is a tourist attraction and a ghost town, but you can still pan for gold (although the only gold I found was fools gold). Pyrite is an iron sulfide mineral and can be found in igneous, metamorphic, and sedimentary rocks which is probably why this rock heavy area was full of it. There are plenty of rock quarries around that you can tell are from miners still searching for gold and our tour guide told us that 200 years ago the surface of the ground was about 65 feet higher, but had been removed by the mining process.
6. Columbia Continued… Garnet I found these little gems while I was panning for gold. In fact there were so many of these little gems that I ended up filling two little vials of them. Garnets are generally red in color but can range from clear to orange to black. Garnets have been used since the “bronze age” and is January’s birthstone. Formation of garnets takes place in metamorphic rock and is commonly found in stones like gneiss and schist. Like most rocks and minerals they too are formed by some sort of process either heat, chemical, or pressures. These probably formed some 20 million years ago when the metamorphic rock they inhabited formed and then was broken away when miners used some type of force like explosives or pick axes.
