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Wednesday, June 29, 2011

The Beach Sand of the Gulf of Mexico under Polarized Light Microscope

Siesta Beach is known as one of the most beautiful beaches in the world. At the "Great International White Sand Beach Challenge" held in 1987, it was recognized as having the "whitest and finest sand in the world."  The sand is so reflective that it feels cool underfoot even on the hottest days. What's the reason? Siesta Beach's sand consists of 99% quartz.
Quartz possess birefringent property which can be examined under polarized light microscope. It can provide an important clue for mineral identification.  The pictures below are the sand collected from the camping trip alone the Gulf of Mexico.  
Siesta beach sand at 20x under polarized light microscope.  The size of the
sands are small and uniform.  Under polarized light microscope, they exhibit
various colors due to different thickness and orientation.









 

Siesta beach sand at 50x under polarized light microscope








 
Crescent beach sand at 20x under polarized light microscope.  Like the
sands collected from Siesta beach.  The sizes of the sand crystal are small
and uniform.








Turtle beach sand at 20x









Sand collected from Henderson Beach, FL









Sand collected from Gulf State Park, AL








Saturday, June 25, 2011

The Beach Sand of the Gulf of Mexico

The beaches on the Gulf of Mexico are famous for their crystal clean water and sugar white sand.  Siesta key beach received numerous awards for its soft, clean, pure-white sand.  The Siesta beach ranks the number one beach in Dr. Beach's top 10 beach list again this year.  Unlike most beaches that are composed of crushed shells, rocks or lava, the powdery sand found on the Siesta Beach is pure white and finer in texture than most refined sugar. Harvard University's geology department found the sand of Siesta Beach was 99% pure quartz.
During the spring break, we had a chance to visit several beaches on the Gulf of Mexico on a camping trip.  We collected some beach sand from each park on the trip (Figure 1): The Gulf State Park, Alabama, Henderson State Park, Florida and Siesta Key, Florida (We visit all three beaches on the key: Siesta, Crescent and Turtle beach).  I check them out on my microscope.  Are they as good as claimed?
Figure 1. Beach sand collection sites on our camping trip

Figure 2. Sand collected from Siesta Beach, FL





























Of all beaches on our camping trip, the sand on the Siesta beach appears to be the whitest.  The sand is also very soft to touch.   It has powdery feel when I rub them between my figures.  The images under the microscope explain the the color and soft touch.  The sand crystals are almost all quartz and completely transparent with very few impurities.  The small and uniform in size also explains the powdery and soft touch.  (Note: The images under the microscope are sparkling. It looks much better than the pictures show - To be fairly compared with other sand specimens, I fixed the ISO and exposure time while taking the picture.  The whiteness of the sand caused the picture to be over-exposed.)
Figure 3. Sand collected from Crescent Beach, FL

On the same key as the Siesta beach, the Crescent beach is slightly to the south of Siesta beach.  The color of the beach sand is almost as white as the sand on Siesta beach and have the same soft, powdery feel.  Under the microscope, they appears almost the same as the sands from Siesta beach.  The slightly more yellowish color is barely noticeable unless I put the picture side by side.
Figure 4. Sand collected from turtle beach, FL

The turtle beach is located on the south end of the Siesta key.  The sand is very dark and  coarse.  There are plenty of sea shells on the beach.  There is no surprise to see that there are plenty of sand made of sea shells.   There are very few quartz crystal found in the sand collected from Turtle beach.
Figure 5 Sand collected from Henderson State Park, FL


Henderson State Park beach is located between Pensacola and Panama city.  The area is famous for its Emerald green ocean.  The sand is sugar white but the sand crystal is more granular than the sand collected from Siesta or Crescent beach.  Like the Siesta or Crescent beach, the sand is almost completely consist of transparent quartz.  The quartz crystal is also larger.
Figure 6. Sand collected from Gulf State Park, AL
The color of the beach on Gulf State Park, AL appears to be more yellowish.  The sand is still be but not as powdery as the sand found on Siesta or Crescent beach.  The sand crystals appear to have more impurities and less transparent. 
Figure 7. Sand collected from Gulf State Park playground
Interesting sand we found in the playground of the Gulf State Park.  There are purple, green and blue particles in the sand.  Out of curiosity, we collected some sand from the play ground and looked at them under a stereo microscope.  They appears to be quartz but stained with different.  The sands seem to have more round edges caused by the weathering.  They appears to be different from the sand collected on the beach.

That's just about my general impression about the same.  Can the number tell me the same story?
The whitenss appears to be consistant with the purity of the quartz crystal found in the beach sand. I took three pictures for each collection by randomly selecting three different areas of the sand specimen.  The number of quartz crystals that are completely transparent, semi-transparent (milk white or yellowish) or none-quartz particles - nice summer project for my kids.  Megan helped out a lot for counting the crystals.
Figure 8. Counting the number of completely particles in the same specimen.  The picture shows the sand specimen collected from Gulf State Park, AL.  The completely clear quartz crystals are striked with green lines while the impurities are circled.
The beach sand collected from Siesta (1142/1149; quartz particles/all particles), Crescent (1144/1152), Henderson State Park (268/270) and Gulf State Park (446/449) beach all have over 99% of quartz.  The percentage goes down to 93% (419 / 449) for Gulf State Park if I only included completely transparent quartz crystals.  The sand from Turtle beach is completely opposite of others.  It contains only 2.5% of quartz (3/114).

Figure 9 Measure the size of particle with TSView image microscope
image acquisition and measuring software
The granunality of the sand can be measured by the size of the sand particle.  Using microscope calibration slide to obtain the conversion factor between pixels and micrometer, I can convert the size of the sand particles in the digital image from pixel to micrometer.  I sampled the particles by drawing a line diagnally and measure the length of any particles across the line.  The average size of the sands from Siesta and Crescent beach (197 and 194 um, respectively) are the smallest among all specimens.  Followed by Gulf State Park and Henderson State Park (386 and 509 um).  The tutle beach sand has the largest average crystal size among all parks (900 um).

Thursday, June 16, 2011

What lives in the flower pot's drainage pan

The drainage pans of the flower pots can easily accumulate water after daily watering or heavy rain.  The nutrients rinsed down from the drainage hole of the flower pot provides good source of energy for microorganisms. It's semi-enclosed space offers year-round environment suitable for microorganism to nurture.  What do I found it the drainage pans of my flower pots?


Two rotifers were trying to gather foods using cilias on the top of the coronas.



The drainage pans of the flower pots are perfect breeding place for mosquitos.

Monday, June 6, 2011

Chucky Gal Mountain Field Trip

We have looked forward to returning to North Carolina for rock hunting since last year's visit to hiddenite gem mine.  The school was just ended couple weeks ago.  We can't miss this GMS field trip to Chucky Gal Knob.  It's a two and half hours drive from metro Atlanta.  Due to the high elevation, it was as hot as Atlanta.

Waiting at the intersection of Hwy 64 and Buck Creek
for other rock hounds to show up.
There are green rock (not showing due to the light condition) 
all-over the place.  The surface is porous caused 
by the weathering.
















Ruby corundum crystals can be found in the green
Smaragdite. 

Another photos of a Ruby Corundum crystal in the 
Smaragdite.  The color of the rubies can be anywhere 
from pink to purple.  There are also some very bright green 
minerals found in the matrix but I am not sure what they are.















Picture show the layer of weathered surface and green 
interior of the smargadite.







Soap stone (Talc)








Another commonly found rock is soapstone.  They are light and form layers.  They are very soft to touch and very smooth to touch.
Some soapstone exhibit green color tone.







Some soapstones are more black in color.







Megan seems to be more interested in the stone in
white color.  In the picture is the milky quartz.







Some Smaragdite on milky quartz.








Although we have not found any ruby of good size but the sprinkles of ruby found in the green Smaragdite already making us very excited about the trip (Some member did find a strip of ruby of finger width.).  Maybe we will hit the jackpot next time.