Hi ma330,
I believe that a coil antenna is best to receive VLF waves and to transmit VLF waves from a portable transmitter or receiver.
But it is possible to use a telescoping antenna for a VLF receiver.
I found a project online to build a small VLF receiver that can tune VLF signals, based on the TDA4100 IC.
This IC has a mixer, VFO, IF amplifier and demodulator unit in one integrated circuit, so there are not too many other parts to add.
This circuit uses all inexpensive parts. And the article tells some substitute parts you can use if the parts are not available.
I do not recommend to use this method for treasure hunting because I do not think you will find any treasure with it.
This project also requires a knowledge of electronics and receivers because there are many options shown in the project.
I cannot give you advice for the best way to build this circuit, but you can look at the article for tips from the person who designed it.
If you want to receive VLF with a telescopic antenna, then this method is working.
See the full article here:
http://www.vlf.it/fritz/pocketrx.html
Best wishes,
J_P