I cured vertigo by taking 1200 mgs of magnesium oxide a day and drinking lots of water. (See How I Cured Vertigo). Magnesium oxide is okay for a short term to correct a deficiency in magnesium, but not good as a long term source.

I needed to find a magnesium that was natural, healthy and suited my lifestyle. This page includes the information I found while I was researching that question.

Magnesium comes from many sources, including clay, dolomite, epsom salt, chalk, nigari and dead sea salt. Add it to liquid and drink, or make it into a pill form. Deficiency symptoms include erratic heartbeat, leg cramps, irritability and muscle weakness.

Calcium and magnesium balance each other, and an excess of one will cause a deficiency of the other. It is suspected that a cause of magnesium deficiency symptoms is eating food that has been "fortified" or "enriched" with calcium, but not adding the vital magnesium to go with it.

Magnesium is refined artificially to make it "purer". There may be exceptions but, in general, any food or nutritional supplement that says magnesium on it will be made with refined magnesium. To get unrefined magnesium straight from the ground that still has its companion and trace minerals with it, you have to get something that is not made for human consumption. Magnesium that is labelled fertilizer or bath grade is probably mined from the earth, but read the label.

Food additive E504 is magnesium carbonate, which can be either mined naturally or created chemically. Food manufacturers who add magnesium carbonate to their food are required to label it with its e-number because it has a laxative effect, but there is no requirement to specify whether it came from natural or artificial sources.

Magnesium carbonate is sold in gyms and athletic supplies as hand-gripping chalk. Also called magnesite.

Magnesium and Iodine
Iodine combines with magnesium to form an insoluble crystal, rendering it unusable by the body, so, if you are taking an iodine supplement and begin to feel dizzy, it would be an indication that you should add magnesium to your supplements, also.

Magnesium and teeth
Although most of a tooth is made of calcium, it is magnesium that makes it hard. Soft teeth that chip easily are a sign of magnesium deficiency.

Magnesium chloride is sold as Nigari to make tofu. NIgari is either refined or natural.  They both come from sea water. The refined means it was bleached and cooked. "Pure" or "food grade" nigari will be refined, although it may still claim to be "natural" or "from sea water". It may be the only way to determine which is which is to look to see if the seller has a long paragraph explaining about their nigari. Those who choose to sell "impure" or "contaminated" nigari will know its true value and will want to talk about it.

Magnesium chloride is also sold in pet stores as an additive for coral reef aquariums, with such names as MagFlake, aquarium sea salt, reef advantage magnesium, Instant Ocean or H2Ocean Pro.

Never Breathe In Magnesium or Any Other Kind of Rock Powder
Sources of Magnesium

Clay (bentonite powder) --You can buy it from a Health Food supplier or dig it up yourself.  Add it to food and beverages or can be used  topically as a mudpack.

Dead Sea Salt  -- 33% magnesium. retail sources use mud from banks.

Dirt -- has absorbable minerals in correct proportion for the human body. Dig some up, put it in a paper bag and keep it for a year to sterilize it without heating it. After that, strain it through a fine sieve to get out the pebbles and add it to food and beverages.

Dolomite lime, magnesium lime or Dolomite -- Considered a superiour source. Take as a supplement. Mix with water or add to food. Sometimes available in garden supply stores in late summer when vegetables need extra magnesium. Best absorbed if taken on an empty stomach and/or with betaine HCl if necessary.

Epsom salts -- magnesium sulfate. Tastes vile. Put in gelatin capsules or use as a bath soak. (Make sure you get same size capsules and filling machine if you get capsules and filling machine).

Gym Chalk -- = magnesite = magnesium carbonate

Nigari -- Magnesium chloride. Used to make tofu, can be ordered online from either Japanese or Chinese specialty or culturing-agent suppliers. Also sold as bath flakes. Main ingredient in "magnesium oil". What's left after sodium is taken out of salt water. An excellent source of magnesium but tastes terrible. Nigari has been used for hundreds years in Japan and China. Nigari is composed mainly of magnesium chloride, but also contains other minerals found in seawater

Sea water -- after it has evaporated for a while, the first crystallization will be of sodium. If this is skimmed off, the remaining water will be very high in magnesium. This is basically the process used in making nigari.

Soapstone -- Mostly talc and rich in magnesium. The marking chalk of sewing (tailor's chalk). 

Talc -- Magnesium silicate. Talcum powder is crushed rock and a source of magnesium. Just be careful not to breathe it in when working with it. It is not soluble in water, but it is slightly soluble in dilute acids.

Organic veterinary sources of magnesium:
Magnesium fumarate (AntaPlus MgF 100), magnesium propionate (AntaPlus MgP) and magnesium acetate (AntaPlus MgA) are "highly-available for the animal due to the organically bound magnesium and consequently effective without delay"

  Types of Magnesium  

• Magnesium acetate -- found in calcium magnesium acetate, a rock salt used as a de-icing agent and added to magnesium supplements for a vegetarian source of magnesium. Highly bio-available, given as a feed supplement to farm animals. Oral
• Magnesium ascorbate -- a buffered form of Vitamin C, available as a supplement in powdered or tablet form. Oral
• Magnesium aspartate --  especially protective therapy against cardiac infarction; has a thrombosis-inhibiting effect
• Magnesium carbonate -- Occurs naturally but can also be synthesized. Often called chalk. Magnesite is the natural form of magnesium carbonate. Not soluble in water so is added to salt to keep it free-flowing. As a food additive it is known as E504 because it can have a laxative effect. As an e-number it is usually artificially produced. Gymnasts' hand grip chalk is natural magnesite in powder form. As with any fine powder, care should be taken not to inhale. Competitive weight-lifting supply outlets will have the most pure, high quality grade chalk.
• Magnesium chloride -- an electrolyte replenisher and for removing waste products such as potassium and urea, as well as free water from the blood when the kidneys are incapable. used in fish tanks, may be found in aquarium pet stores. (add iodine to make a claimed cancer cure), the chloride will be used by the body to make stomach acid (Hcl).Oral

• Magnesium citrate -- good but irritating, a saline laxative used for bowel evacuation before diagnostic procedures or surgery of the colon. thrombosis-inhibiting effect. Recommended for neuralgia. Oral
• Magnesium fumarate -- Highly bio-available, given as a supplement to farm animals.
• Magnesium gluconate -- recommended for neuralgia. easily absorbed. Oral
• Magnesium glycinate  -- an amino acid chelate. easily absorbed. Good for people with heavy metal poisoning such as mercury if taken for a short term but may cause cardiac arhythmias if taken for long periods. Discontinue if heartbeat becomes irregular. Oral
• Magnesium hydroxide -- on the bottom of a limewater reservoir. caustic, Milk of Magnesia. The solid mineral form of magnesium hydroxide is known as brucite. Mag hydroxide as milk of magnesia can be made into magnesium bicarbonate by mixing it with carbonated water (seltzer). Since ale is carbonated water, it should work with fermenting, too.
• Magnesium lactate -- easily absorbed Oral
• Magnesium malate -- very good, the malate part is good for the Krebs Cycle of the body. Malate may be good for ridding the body of aluminum. Used for fibromyalgia and body building. Recommended for neuralgia. Oral
• Magnesium orotate (dihydrate) -- easily absorbed. is considered a superior form. Orotates are the mineral salts of orotic acid (vitamin B13, manufactured in the body by intestinal flora.) Long­term therapy against cardia infarction. Transports the magnesium atom to the membranes of the cell. Orotic acid is found in root vegetables and whey. Oral
• Magnesium oxide -- Inorganic, some recommend it is not to be taken internally, though it is the most likely form that will be prescribed by an allopathic MD for a low magnesium diagnosis.. It is very poorly absorbed. It primarily functions as a laxative.
• Magnesium peroxide  --  potentially damaging tissues
• Magnesium propionate -- Highly bio-available, given as a supplement to farm animals.
• Magnesium silicate --  white powder practically insoluble in water. talcum powder, soapstone, French chalk powder.

• Magnesium stearate -- contains stearic acid, an 18 carbon long saturated fat, metabolized to oleic acid (the monounsaturated fat found in olive oil) Bad mouthing magnesium stearate is nothing more than a sales pitch.
• Magnesium succinate - Oral
• Magnesium sulphate -- Epson Salts -- used as a laxative. Not absorbed orally but can have an antibiotic effect. Some absorbtion topically. more appropriate for soaking. Excess use of magnesium sulphate will also cause a boron imbalance

  Make Your Own Magnesium Supplements  

If you are experiencing symptoms of magnesium deficiency, probably any type of magnesium, even the bad ones, will help, but after you are no longer suffering a magnesium deficiency-related condition, you need to think about what type of magnesium to take to maintain that. Magnesium is said to be either "natural" or "synthetic", but the distinction between the two isn't always clear and there is no help to be obtained from any government label regulations. Because there is no public demand for clarity, the government goes along with industry demands for designations, which are sometimes difficult to interpret.

 Food Sources of Magnesium 

Wheat germ; unmilled grains such as whole wheat and brown rice; pumpkin, sunflower, and other seeds; cocoa; chocolate; unblanched almonds and filberts; rice bran; beans; lentils; tofu; spinach; halibut; and mackerel.

Oxalic acid in vegetables such as spinach and chard and phytic acid in some grains may form insoluble salts with magnesium, causing it to be eliminated rather than absorbed.

.Issues 

• Doesn't this contain lead? Any natural magnesium mined from the soil will contain trace elements of lead, as does soil  The only lead-free source of magnesium will be artificially manufactured in the lab. The presence of lead in magnesium is mostly made an issue of by people selling processed magnesium. Lead is most likely a trace element that we need in minute amounts from an organic source and is only toxic when it is taken in in large amounts from inorganic sources.
• Magnesium oil is magnesium chloride reduced from salt water to at least a 25% concentration, which will have a slightly oily feel to it. Commercial magnesium oil is usually magnesium chloride mixed with some oil to dilute it.
• At one time, magnesium chloride was used as an antibiotic.
• Enteric coating on any magnesium supplement (to make it easier to swallow) can decrease bioavailability.
• Garden lime or pickling lime (same thing) -- is calcium hydroxide or garden lime. It contains magnesium but in less than the desired 2:1 ratio. OK to eat but not enough magnesium. A good choice to add to food if you are supplementing with magnesium pills but not taking any extra calcium, as it will have all the other natural minerals that both minerals need to function properly. This dissolves well in water and can be added to food or beverage. Can be added to fermented pickles but remember to use enough salt and ideally a starter from a previous batch because it sweetens the ferment making it more desirable to unwanted microbes.
• Once upon a time there was a government study that showed that stearic acid reduced the immune response. It had all the usual flaws of government studies, but there are those who claim that magnesium stearate is bad for you based on the study.

• Orally-consumed magnesium is often less effective because the body tends to eliminate it quickly, whereas topically applied magnesium is absorbed directly into muscles and other tissues. Another advantage to topical application is that the body seems to know how much to absorb, and it appears to adjust its rate of absorption depending upon its immediate needs.

• Magnesium is a muscle relaxant, while calcium is a muscle constrictor. You should consume about 2 parts calcium to each part magnesium you supplement. The easiest way to do this is through natural sources of magnesium such as powdered dolomite, clay or brine sea salt that have the correct proportion. The best way is to get it from plant sources with bromelain added. A reasonable compromise is to do a little of both. An ideal situation would be to fertilize your garden with powdered dolomite (also known as dolomite lime) and grow your own food on it.

• Decreases in magnesium intake have been more prevalent in western diets with the addition of supplemental calcium and refined or processed carbohydrate foods.
• Magnesium requires an acidic stomach environment for best absorption, so taking it between meals or at bedtime is recommended. The acid in our stomach is hydrochloride so any mineral with chloride in its name will help make stomach acid.
• Meals high in protein or fat or a regular diet high in phosphorus or calcium (which can compete with magnesium) may decrease magnesium absorption.
• Natural nigari is extracted from sea water by removing most or all of the sodium chloride and water. It contains primarily magnesium chloride plus all the other salts and trace minerals naturally found in sea water, as well as twigs, sand, plankton, organic matter, etc. Japanese nigari is usually synthesized, Chinese production of  nigari continues to be extraction from sea water.
• Food grade magnesium chloride made in the U.S. is produced from the reaction between hydrochloric acid and magnesium.
• Asbestos is a form of magnesium, and may be a good form of magnesium for all I know, as long as you don't breathe it in, which is true of any rock powder. I'm not going to recommend it here because of its issues, but I mention it in case someone says that other forms of magnesium like talc or soapstone are similar to asbestos. It is in fact true. I  don't think it's a big deal, but don't breathe it. Talcum powder was also found to cause cancer in test animals forced to breathe it in 6 hours a day.
• Gypsum -- is calcium. It's okay to eat but it's not magnesium (that is, it contains some magnesium but not enough to be suitable for supplementation.)
• Quicklime and Slaked Lime -- actually are magnesium but dangerous. Quicklime is produced by burning rock limestone in kilns. It is highly caustic. Quicklime reacts with water to produce slaked, or hydrated, lime, thus quicklime is spread around the land in heaps to absorb rain and form slaked lime, which is then spread on the soil. Their use is prohibited by organic standards