Subject: Why is there such a large difference between sand and air temperature

Why is the temperature difference between the air and the sand so large in 
deserts.the air temperature is around 45 ° C and sand around 15 ° c higher on  
hot days.And the sand temperature is 5 to 15 ° C lower than air temperature at 
nights.And is the high temprature of sand due to the mineral 
(lime,borax,alkali) content in the day time?And does this make sand a good 
solar heat absorber?

Re: Why is there such a large difference between sand and air temperature