What are the shar’i ways of extracting rikaz?
Question

What are the shar’i ways of extracting the treasures of the earth – rikaz?.
Praise be to Allah.rikaz refers to what is buried in the earth of the wealth of the Jaahiliyyah. The people of the Jaahiliyyah are the ones who existed before the coming of the Prophet (peace and blessings of Allah be upon him), no matter what religion they followed. Islam has enjoined that when it is extracted, the khums be paid on it, as zakah according to some scholars and as fay’ according to others. The rest belongs to whoever extracted it, if it was extracted from land that he owns, or from ruins or common land such as the street and so on. 
Ibn Qudaamah al-Maqdisi (may Allah have mercy on him) said: 
rikaz is that which is buried in the earth, and the word is derived from the root rakaza … From this root is also derived the word rikz, which means a hidden voice or whisper. Allah says (interpretation of the meaning): “or hear even a whisper [rikzan] of them” [Maryam 19:98]. 
The basic principle concerning the zakah on rikaz is that which was narrated by Abu Hurayrah from the Messenger of Allah (peace and blessings of Allah be upon him): “There is no compensation for damage done by animals, and the khums is due on rikaz.” Agreed upon. 
There is also scholarly consensus on this matter. Ibn al-Mundhir said: We do not know of anyone who disagreed with this hadeeth except al-Hasan who made a distinction between that which is found in dar al-harb and that which is found in the land of the Arabs. It was said that the khums is due on that which is found in dar al-harb and zakah is due on that which is found in the land of the Arabs. Al-Mughni (2/610) 
Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allah have mercy on him) said: 
Not everything that is buried is rikaz, rather it is everything that was buried during the Jaahiliyyah, and what is meant by the Jaahiliyah is before Islam, for example, if we find buried treasure in the earth, and we extract it and find on it signs of the Jaahiliyyah, such as money which is known to come from a time before Islam, or there is a date on it that is before Islam, and so on. 
“The khums is due on it whether the amount is small or large” means that there is no condition of nisaab (minimum amount), because of the general meaning of the words of the Prophet (peace and blessings of Allah be upon him): “The khums is due on rikaz.” 
But the scholars differed concerning the khums – does it come under the heading of zakah or fay’? This is based on their difference of opinion concerning the definite article al- in the words of the Prophet (peace and blessings of Allah be upon him) in the hadeeth, “The khums (al-khums)” – does it serve to define the amount that is due on it or is just confirming that which is established, which is that anything that is fay’ is subject to the khums? 
Some of the scholars said that it is zakah, so the al- is defining the amount that is due on it. 
This view implies the following: 
1-That the rate of zakah on rikaz is higher than the rate on other kinds of wealth that are subject to zakah, because half of one-tenth, one-tenth, a quarter of one-tenth, and one sheep out of every forty are all less than one-fifth (the khums).
2-The nisaab is not a condition, so the khums must be paid on a little or a lot.
3-It is not essential that it be of a specific type of wealth. The khums must be paid on it whether it is gold, silver or other metals, unlike other kinds of zakah.
The correct view according to our companions – may Allah have mercy on them – is that it is fay’, so the al- in al-khums is confirming that which is established, not defining the amount that is due on it, i.e., it is the khums that is known in Islam, and it is the khums on booty which is fay’, which is to be spent in the public interests of the Muslims. This is the more correct view, because regarding it as zakah goes against what is known about zakah, as has already been explained in the three previous answers. 
Al-Sharh al-Mumti’ (6/88, 89). 
If a person finds rikaz on which there are no signs to indicate whether it was buried during the Jaahiliyyah, it comes under the heading of luqtah (lost property). He should wait for a whole year, then it is permissible for him to take possession of it after that, unless he finds out for sure who its owner is, in which case he must give it to him, or compensate him by giving him its value at the time when he disposed of it. 
It is not permissible to look for treasure in land that belongs to anyone, because this is disposing of another person’s wealth unlawfully. Whoever finds wealth in land belonging to someone else must give it to the owner of the land. 
Sensible people should not waste their lives looking for such treasure, because it is a waste of time and wealth, in addition to the fact that it results in penalties imposed by the state. A man may spend his whole life and not find a single coin, and another man may work in farming and tilling his land, then Allah may bless him with finding something that will make him free of want for the rest of his life. 
Secondly: 
Many people employ means that are not acceptable in sharee’ah for extracting this treasure. Some of them seek the help of magicians, soothsayers and other charlatans, others rely on their contact with the jinn. All these methods are unacceptable in Islam and constitute grave sins. 
Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allah have mercy on him) was asked:  
There are people who summon the jinn by means of incantations, and they make them extract treasure that has been buried in the town’s land since ancient times. What is the ruling on this action? 
He replied: 
This action is not permissible. These incantations by means of which they summon the jinn and employ them are – in most cases – not free of shirk, and shirk is a serious matter. Allah says (interpretation of the meaning):  
“Verily, whosoever sets up partners (in worship) with Allah, then Allah has forbidden Paradise to him, and the Fire will be his abode. And for the Zaalimoon (polytheists and wrongdoers) there are no helpers”
[al-Maa’idah 5:72]
The one who goes to them tempts them and encourages them; he makes them think that what they are doing is right and he tempts them by means of the money that he gives to them. 
We should boycott these people and stop going to them, and warn our Muslim brothers against going to them. In most cases these people trick the people and take their wealth unlawfully, and tell lies. If (their predictions) happen to coincide with the divine decree, they start to broadcast it among the people, saying “We said such and such and it happened,” but if it does not happen, they make false claims and say that this is what prevented it from happening. 
I offer the following advice to those who are suffering with this matter: Beware of telling lies to the people and associating others with Allah, may He be glorified and exalted, and taking people’s wealth unlawfully, for the end of the world is nigh and the reckoning of the Day of Resurrection is severe. You have to repent to Allah from this deed, and ensure that your deeds are correct and your wealth is halaal. And Allah is the Source of strength.  
Fataawa al-Shaykh Ibn ‘Uthaymeen (2/question no. 116) 
You should understand that what makes many people pursue these illusions and seek them from the magicians and charlatans etc is the love of luxury and their longing for riches, without implementing the means of becoming rich, and seeking wealth in inappropriate ways, as well as their laziness and inclination towards idleness.  
Ibn Khuldoon (may Allah have mercy on him) said:
What makes people do that in most cases, in addition to their naivety, is an inability to seek a living in the normal ways such as earning through trade, agriculture and handicrafts, so they seek it in deviant ways and unnatural ways, because they are not able to strive to earn a living and they do not want to work hard for it. They do not realize that they are letting themselves in for trouble by seeking wealth in inappropriate ways, and they expose themselves to punishments, and their motive for that is their extreme love for a life of luxury, which a regular way of earning would not be able to support.
So when a person fails to earn a living in the natural manner, his only answer is to wish to have great wealth in one go, without making any effort, in order to support the way of life to which he has become subservient. Hence you will find him very keen and doing his utmost to earn money in that way.  Therefore you will see that most of those who strive for that are those who are living a life of luxury of the ruling class and those who live a life of ease in the cities such as Egypt etc. So you will find many of them very keen to seek wealth in that manner, and they ask people coming from other cities and countries about possible sites of treasure. 
Muqaddimat Ibn Khaldoon (p. 385, 386) 
Ibn Khaldoon wrote a valuable chapter on this in his Muqaddimah (pp 384-389). 
But if the Muslim avoids haraam ways such as incantations, seeking the help of the jinn, magic and soothsaying, or transgression against the property of others, such as land, houses and so on, then there is no sin on him if he finds any of that buried treasure, and there is no sin on him if he seeks it and looks for it, if he has knowledge of the ways of looking for it, and he does not waste his life in running after mirages and dreams of treasure, like those in the past who used to seek to turn metals into gold by means of alchemy, and it was said of them: The one who seeks wealth by means of alchemy will become penniless. 
But to suggest that there is a shar’i way of looking for it, this is not correct because Islam did not come to explain such matters, rather it came to explain what is permitted and what is forbidden. 
With regard to tools and things that people have invented to find out about it by physical means and indications, that is permissible for the one who learns about it and uses it. 
And Allah knows best.