Well the 'truth" is that all reality is subject to consciousness. Also all people are different.
There are MANY people and MANY books that not only believe all of this but have also experienced it. It is possible that it is simply a placebo but the only thing that matters is if it works.
You can experiment by getting some precious stones and meditating with them. See if you can feel the influence.
I my self love stones and feel they benefit me.
What is undeniable is that precious stones and metal have a real store of value and will likely increase over time and supply decreases and demand increases.
Thanks for the comment.