1. Blue Diamond – $3.93 million per carat
Blue diamond is a type of diamond which exhibits all of the mineral ‘s inherent properties except with the stone’s additional element of blue colour. They are colored blue by trace amounts of boron which contaminate the structure of the crystalline lattice. Blue diamonds belong to a diamond subcategory called fancy color diamonds, the generic name for diamonds displaying intense colour. Blue diamonds range from Flawless to Included in grade as is the case with white diamonds.
The diamond, named “The Oppenheimer Blue” in honor of its previous owner, sold for a final price of $57.5 million. While the Pink Star diamond broke its record for most expensive jewel ever sold, the blue diamond holds the record for the most valuable price per carat at $3.93 million.
2. Jadeite – $3 million per carat
Jadeite is the purest, rarest, and most vivid gemstone in the Jade family. Jadeite is a pyroxene mineral with composition NaAlSi2O6. It is monoclinic. It has a Mohs hardness of about 6.5 to 7.0 depending on the composition. The mineral is dense, with a specific gravity of about 3.4.
The “Hutton-Midivani Necklace”, which consists of 27 large, top quality jadeite beads, did just that. After twenty minutes of intense bidding from eight potential buyers, the piece sold for $27.44 million to Cartier, the original designer of the necklace.
3. Pink Diamond – $1.19 million per carat
Pink diamonds are extremely rare. Only 0.0001% of the diamonds in existence are pink. It is a gemstone that would give beauty and harmony to the world. Just like white diamonds, pink diamonds can range from flawless to (heavily) included. The Pink Star is the only pink diamond in the world that is completely flawless.
In 2017, a stunning pink diamond weighing 59.60-carats was sold at a Sotheby’s auction in Hong Kong for a record-breaking $71.2 million. That’s $1.19 million per carat. Known as the “Pink Star” diamond, it’s the largest Fancy Vivid Pink diamond ever graded as Internally Flawless by the Gemological Institute of America.
4. Red Diamond – $1,000,000 per carat
Red Diamond is a diamond with the same mineral properties as colorless diamonds, displaying red color. They are commonly known as the world’s most expensive and rare color of diamonds, more so than pink diamonds or blue diamonds.
It is like pink diamonds, are highly debated as to the source of their color, but the gemological community most frequently attributes both colors to gliding atoms in the structure of the diamond as it undergoes tremendous pressure during its formation.
5. Emerald – $305,000 per carat
Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor.
At the Christie’s auction, it was purchased for $5.5 million, or $305,000 per carat. That made it the most expensive emerald per carat ever sold.
6. Taaffeite – $35,000 per carat
Taaffeite BeMgAl4O8 is a mineral named after its discoverer Richard Taaffe (1898–1967) who found the first sample, a cut and polished gem, in Dublin , Ireland, in October 1945. As such, this is the only gemstone that was first identified from a faceted stone. Most of the gem pieces had been misidentified as spinel, prior to Taaffe. It was only known in a few samples for many years after, and it is still one of the world’s rarest gemstone minerals.
Chemical and X-ray analysis confirmed taaffeite ‘s main constituents as beryllium, magnesium and aluminum in 1951, making taaffeite the first mineral to contain both beryllium and magnesium as essential components.
The confusion between spinel and taaffeite is understandable, as certain structural characteristics in both are identical. Anderson et al., classified taaffeite as a spinel-to-chrysoberyl intermediate mineral. Unlike spinel, taaffeite displays the double refraction property which allows distinguishing between these two minerals.
7. Grandidierite – $20,000 per carat
Grandidierite is a rare mineral originally discovered in southern Madagascar in 1902. The mineral was named to honor French explorer Alfred Grandidier (1836–1912) who studied Madagascar’s natural history.
The more iron (Fe) they contain, the more grandidierites appear bluer in colour. The Fe-analog (Fe, Mg) to grandidierite (Mg, Fe) is a recently discovered gemstone, blue ominelite.
Grandidierites display strong trichroic pleochroism. That means that depending on the viewing angle, they can show three different colors: dark blue-green, colorless (sometimes very light yellow), or dark green.
8. Serendibite – $18,000 per carat
Serendibite is an extremely rare mineral of silicate first discovered by Dunil Palitha Gunasekera in Sri Lanka in 1902 and named after Serendib, the old Arabic name for Sri Lanka.
The mineral is found in skarns associated with boron metasomatism of carbonate rocks where intruded by granite. Minerals occurring with serendibite include diopside, spinel, phlogopite, scapolite, calcite, tremolite, apatite, grandidierite, sinhalite, hyalophane, uvite, pargasite, clinozoisite, forsterite, warwickite and graphite.
9. Diamond – $15,000 per carat
In mineralogy, diamond is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at standard conditions.
Diamond is renowned as a material with superlative physical qualities, most of which originate from the strong covalent bonding between its atoms. In particular, diamond has the highest hardness and thermal conductivity of any bulk material. Those properties determine the major industrial application of diamond in cutting and polishing tools and the scientific applications in diamond knives and diamond anvil cells.
10. Black Opal – $15,000 per carat
Australian black opals are the most valuable and widely known type of opal. Black opal is characterised by a dark body tone which can range from dark grey to jet black. (See the following chart). However this refers only to the general body tone of the stone, and is not related to the rainbow or spectral colours present in the opal. Some people expect a black opal to be completely black (in which case it would be completely worthless).
Unlike ordinary opals, black opals have carbon and iron oxide trace elements present, which cause the unusual darkness of the stone. Because of their dark body tone, the rainbow colours in a black opal stand out much better than lighter opals.
By comparison, black opals are the most valuable form of opal – due to their dark body tone and the resulting vibrant play of colour. Top of the range gem quality black opal can fetch prices up to AUD $15,000 per carat. However, just because an opal is black doesn’t make it valuable. There are many factors including brightness and pattern which determine the overal value of opal. Read more in our article on the value of opal.
11. Alexandrite – $12,000 per carat
Alexandrite (BeAl2O4) is a type of chrysoberyl found during the 1830’s in the Ural Mountains, Russia. You may have seen this mineral ‘s incredibly changing color where it seems to be emerald in light and ruby red in darkness.
The variety of alexandrite shows a change of color depending on the nature of ambient lighting, called metamerism. Metamerism is the phenomenon of an observed change in color from greenish to reddish with a change in source illumination. Alexandrite results from the small-scale replacement of aluminum by chromium ions in the crystal structure, which causes intense light absorption over a narrow range of wavelengths in the yellow region (580 nm) of the visible light.
12. Red Beryl – $10,000 per carat
Red beryl (formerly known as “bixbite” and marketed as “red emerald” or “scarlet emerald” but notes that both latter terms involving “Emerald” terminology are now prohibited under the Federal Trade Commission Regulations in the United States) is a red variety of beryl. It was first described at Maynard ‘s Claim (Pismire Knolls), Thomas Range, Juab County, Utah, for an occurrence, its type locality, in 1904.
Red beryl is very rare and has been reported only from a handful of locations: Wah Wah Mountains, Beaver County, Utah; Paramount Canyon and Round Mountain, Sierra County, New Mexico, although the latter locality does not often produce gem grade stones; and Juab County, Utah.
13. Musgravite – $6,000 per carat
Musgravite or magnesiotaaffeite-6N’3S is a rare oxide mineral used as a gemstone. Its type locality is the Ernabella Mission, Musgrave Ranges, South Australia, for which it was named following its discovery in 1967. It is a member of the taaffeite family of minerals, and its chemical formula is Be(Mg, Fe, Zn)2Al6O12. Its hardness is 8 to 8.5 on the Mohs scale. Due to its rarity, the mineral can sell for roughly USD$35,000 per carat.
14. Benitoite – $4,000 per carat
Benitoite is a rare blue titanium cyclosilicate barium, found in serpentinite altered by hydrothermal conditions. It forms at convergent plate boundaries in low temperature , high pressure environments typical of the subduction zones. Benitoite fluoresces under ultraviolet light of short wave, which appears bright blue to bluish white in colour. The more rarely seen clear to white benitoite crystals fluoresce red under long-wave UV light.
Benitoite typically occurs with an unusual set of minerals, along with minerals that make up its host rock. Frequently associated minerals include: natrolite, neptunite, joaquinite, serpentine and albite.
Benitoite is a rare mineral found in very few locations including San Benito County, California, Japan and Arkansas. In the San Benito occurrence, it is found in natrolite veins within glaucophane schist within a serpentinite body. In Japan, the mineral occurs in a magnesio-riebeckite-quartz-phlogopite-albite dike cutting a serpentinite body.
15. Poudretteite – $3,000 per carat
Poudretteite is an extremely rare mineral and gemstone that was first discovered as minute crystals in Mont St. Hilaire, Quebec, Canada, during the 1960s. The mineral was named for the Poudrette family because they operated a quarry in the Mont St. Hilaire area where poudretteite was originally found.
16. Fire Opal – $2,300 per carat
Fire opal is a translucent opal with warm body colors ranging from yellow to orange to gold. Even though it usually doesn’t show any color play, sometimes a stone will show bright green flashes. Querétaro in Mexico is the most popular supplier of fire opals; these opals are commonly referred to as Mexican fire opals.
Opal is a hydrated amorphous type of silica (SiO2·nH2O); its water content can differ by weight from 3 to 21%, but is typically between 6 and 10%. It is known as a mineraloid because of its amorphous nature, unlike crystalline types of silica, classified as minerals. It is deposited at a relatively low temperature and can occur in nearly any rock fissures, most commonly found in limonite, sandstone, rhyolite, marl, and basalt. Opal is Australia’s largest gemstone.
17. Jeremejevite – $2,000 per carat
Jeremejevite is a rare aluminium borate mineral with variable fluoride and hydroxide ions. Its chemical formula is Al6(BO3)5(F,OH)3.
It was first described in 1883 for an occurrence on Mt. Soktui, Nerschinsk district, Adun-Chilon Mountains, Siberia. It was named after Russian mineralogist Pavel Vladimirovich Eremeev (Jeremejev, German) (1830–1899).
It occurs as a late hydrothermal phase in granitic pegmatites in association with albite, tourmaline, quartz and rarely gypsum. It has also been reported from the Pamir Mountains of Tajikistan, Namibia and the Eifel district, Germany.