Will a microwave heat sand? I want to cook Turkish coffee on heated sand at school. I have difficulty accessing some easier method of heating, so I was going to try to heat sand in a microwave. It was then pointed out to me that sand, unlike water-dense foods, does not conduct electricity.
Will sand be heated by a microwave?
 A: Well, I just put an empty glass plate in the microwave for 20 seconds and it did heat up ( hotter than my hand, maybe 40C), so people who think that silica does not absorb microwaves are wrong, at least for my microwave oven. I often heat up coffee in a glass, and the handle gets hot too, I was not sure it was not conduction from the coffee, so I tried the plate.
So I will agree with the other experimenter, Rob N, that sand which is mostly silica will heat up in the microwave.
Your problem then would be: to what temperature, as you will need  excess of 100C to  bring to a boil a turkish coffee. I think it will work, glass plates get really hot in the microwave.
A: Dielectric heating is the priciple of a microwave oven. Water $H_2O$ has a strong dipole moment.

Since the water molecule is not linear and the oxygen atom has a higher electronegativity than hydrogen atoms, the oxygen atom carries a slight negative charge, whereas the hydrogen atoms are slightly positive. As a result, water is a polar molecule with an electrical dipole moment.

The sand in your microwave absorbs the power density (per volume)
$$\frac{P(f)}{V} = 2\pi\epsilon_0E^2\cdot\epsilon''_r(f)\cdot f$$
$$\approx const \cdot\epsilon''_r(f) \cdot f$$
Sand (partly consisting of silica $SiO_2$ and small rocks) has a smaller dipole moment. 
Water has a real part of relative permittivity of $\epsilon_r(20°C)=80.1$, while silica has $\epsilon_r=3.9$. I haven't found their imaginary part $\epsilon''_r$. The imaginary part of relative permittivity $\epsilon''_r$(f)  essentially is the absorption and is dependant of the frequency. 
$$\epsilon''_{\text{water}}(2.45\,GHz) > \epsilon''_{\text{sand}}(2.45\,GHz)$$
Microwave ovens at home have a certain field strength of $E$  use a frequency of $f=2.45\,GHz$.
Exact values depend on the type of sand and should be edited in here.
A: I did heat sand up this morning in my little office microwave, I threw out my back and was looking into making a heat source to put on it, not have much out the office that I thought would work, I tried sand, ran some magnets through it to make sure there was no metal of any kind in it, it was all good, so this is what I did 
1 - cut the strap off a junk back pack, then cleaned out the inside 
2 - Taking sand I bought from Home Depot I filled up the strap with sand and zip tied it shout, leaving room inside for it tot move around
3 - place in the microwave and heated it for 30 second burst until I was happy with the heat it was producing
Seems to be working fine at the moment 
Sad to say I had the "hey what if" in me doing this before ANY research was done, but it seemed to work fine so I guess I got lucky, LOL :)
A: There is evidence which shows that only certain kind of sand gets heated up. And if you microwave them they will acquire the strength of the rock . We can't say sand does not heat up.
A: Clear glass doesn't heats up at all. Sand molecules are quartz and doesn't have dipoles so it shouldn't heat up. But molecules does absorb electromagnetic waves. So it may absorb a very small fraction of it.
A: I would not experiment with a microwave oven without a decent load inside. Wet sand could work if you cook out the water. Note that the sand will reach 100 degrees at most and will cool off rapidly by evaporation of any remaining water once outside the oven. To make coffee you will probably need stable sand temperatures at or above 100 degrees and no rapid cooling. I am just guessing as I use the old fashioned filtration method myself. 
A: I assume that when you say 'microwave' you are talking about a microwave oven. As you say sand unlike water dense foods cannot conduct electricity. But in a microwave the foods are not heated up using electricity but by bombarding it with microwaves. The microwave use electricity to generate microwaves of frequency 2.4 GHz. In your question you have already said that sand is being heated up at your school. It is happening due to the light radiation  being received by the sun. Microwaves are also a type of electromagnetic radiation like light. When light radiation is capable of heating up the sand then microwaves can also heat up the sand kept in the microwave oven.
