San Clemente, CA beach sand . Although this light-colored sand appears tan to th

Question

San Clemente, CA beach sand. Although this light-colored sand appears tan to the naked eye (Fig. 2), most of the grains are colorless under the microscope. The composition of this sand is similar to the composition of the granitic rocks found in nearby mountains, mainly minerals such as feldspar, quartz, and biotite. What does the presence of the mineral biotite (think about the weathering sequence and the physical properties of biotite) suggest how much these grains have been weathered and transported?

Explanation / Answer

Biotite are dark color mineral and have an hardness of 2.5-3 and it’s elastic in nature and they appears to be transparent to translucent in nature, and when considering its formation temperature it’s quite high and considering to the stability of the minerals it’s given by

1. IronOxide, Alumminium Oxides

2. Quartz

3. Clay minerals

4. Muscovite

5. Alkali Feldspar

6. Biotite

7. Amphiboles

8. Pyroxenes

9. Ca-rich plagioclase

10 Olivine.

When looking at the list iron oxide is most stable where as the Olivine is list stable where as the Biotite is in between this. Where as the weathering of the biotite result in the development of clay minerals. The small amount of presence in the Quartzo-Feldspathic sediment indicates it has been weathered in less amount and most of the grains would have converted into clay minerals during the transportation or from the deposition site.

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