The pratikool-anukool theory making rounds and giving certificates to each and all on payment of some money, does not hold ground, as you will read in the following lines submitted by me.
a) Should we recommend gemstones for functional malefic planets? functional benefic planets only? or Both?
b) Should we recommend gemstones for planets placed in 6th, 8th and 12th Houses? In which conditions?
Normally not. But essentially if these planets placed in 6th, 8th or 12th are placed in nakshatras who are owners of the wealth giving houses or desire fulfillments(2nd and 11th ). (Which is what one requires in Life, so lets be honest here).
c) Should we use Divisional charts for recommending gemstones instead of Rashi chart? For example: Dashamsha for Career?
d) Should we recommend precious and semi-precious gemstones and leave the decision to the user to decide which one to wear?
Yes. (I personally do not recommend semi-precious)
e) Should we recommend gemstone only for the lords of Lagna, 5th and 9th? If so, why not others, if they are benefic and placed well?
The 9th if a badhaksthana for a Fixed Lagna must not be recommended. One must not suggest Lagna Lord Gem if it is placed in nakshatra of the planet owning 8th or 12th. Because then the Lagna Lord will be actually giving the results of these negative houses. For a person who is in service the Gemstone for the 5th lord should not be recommended because then he may begin facing problems in his job, since the job is signified by the 6th house and by wearing the Gemstone for the 5th Lord one is actually strengthening the 12th house from the 6th.
BUT for a person looking for good health , he must be suggested a Gemstone for the 5th Lord, because the 5th signifies Cure.
So there are Gemstones to be recommended for a specific purpose too depending on the current problem. For instance one not getting a job if badly looking for one, may be suggested a Gemstone for the planet signifying the 6th Lord, but eventually after acquiring one, has to remove the same, or else would also increase the ill health propensities in his nativity.
Even the Lord of the 8th can give superb results if well placed, and even the Lord of the Lagna can give bad results, so there is nothing like some mandatory rule to be followed in this matter.
f) Which gemstones do you recommend for each planet? Example: Red Ruby and Red Garnet for Sun. Emerald, Peridot, Green Jade for Mercury.
The Original Gemstones. Ruby and Emerald. If the person cannot afford this, then let him keep the objects of the planets in his Shirt Pocket, like piece of Haldi , or some sugar for the Moon etc.
Gemstone recommending is an intricate science but now has become a like a Duplicate Rolex watch in hands of one and all.
At times Gems have to recommended for a temporary time, keeping the end(Result) in mind and once that is achieved,the Gem must be removed.
At times if one is not able to marry then one has to be suggested Gemstone for Planet signifying 2nd and 7th but would you allow the person to wear this, till he becomes old, when this same Gemstone would tend to strengthen to the maraka propensities for the native ?
The there are other problems to contend with too. For a newly married couple a green Emerald will not be favourable. Why ? Because it will reduce the sexual desires. Remember the basics ? Mercury is a Hermaphrodite Planet .
Then there are people who at the drop of the hat suggest The Pearl or the Moonstone immediately. Now if the Sun is the Lord of the Kundli or having Lordship of an imposrtant house in the Horoscope, would it make sense to wear a Pearl ? Or else if one is born on a Amavasya or a Poornima one should certainly note what would be the effects of wearing a Pearl before jumping to suggest this. There are other factyors like waning Moon and the waxing Moon the implications of which must be understood well before suggesting this Gem. Instead of bringing stability to mind, on the contrary it may cause depressions too. And by the way nobody in Real Life is so unstable that we need to suggest Gems for such frivilous matters which most astrologers do. “Your mind will become calm. You will be able to make better decesions. You will have peace of mind”. This is logicless talking. Because the other problems which may affect in a horde, would not be foreseen or one may not have the foreseight to observe these.
Even the above made suggestions would change strictly speaking if one goes for Original Cosmic colour therapy ,on which I wil put a note some other day or may not put up because its too exhaustive and technical. For Instance we think that the Pearl means white, but actually its Cosmic rays are made of Orange colour. We think Diamond as White but its Cosmic rays are of Indigo colours. If one has excess of Red(Pitta) Cosmic rays in his body then one has to counter it with Orange/Green(Kapha) Rays. This is related to the various Chakras in the body. For instance the Red Colour (Fire Element) represented by Ruby, rules the Manipur Chakra in the body , also known as the Solar/Abdominal Plexus. This will be affecting the Pranamaya Kosha. All the Gems are nothing but a Concentrated form of the Cosmic rays (like Gulab Jala made of Rose, or Vanilla Essence), and each Ray is linked to a particular wavelength (For ex. Red has a Wavelength Mu of 800-650) which affects the body, so wanton suggestion of Gems is a dangerous habit and carries a lot of rinabandhan on the Astrologer suggesting so.