10 most difficult minerals riddles

Of the 10 largest silver mines in the world, three are located in Mexico and three in Poland. The remaining four are in China, Peru, Bolivia and Turkey.

Moissanite is regarded as a diamond alternative, with some optical properties exceeding those of diamond. Its lower price and less exploitative mining practices necessary to obtain it make it a popular alternative to diamonds. Due in part to the similar thermal conductivity of moissanite and diamond, it is a popular target for scams; however, higher electrical conductivity and birefringence of moissanite may alert a buyer to fraud.

Despite their name, rare-earth elements are – with the exception of the radioactive promethium – relatively plentiful in Earth's crust, with cerium being the 25th most abundant element at 68 parts per million, or as abundant as copper. They find application in the most dynamically developing areas of high technology industry such as: aviation, space flights, production of mobile phones (smartphones).

Garnets come in a variety of colors and have many different varieties, except blue. The most widely-known color of Garnet gemstones is dark red. When the term "Garnet" is used, it is usually connotative of the dark red form.

The Cullinan Diamond is the largest gem-quality rough diamond ever found, weighing 3,106.75 carats (621.35 g), discovered at a mine in Cullinan, South Africa, on 26 January 1905. It was cut into 105 diamonds including the Great Star of Africa, 530.2 carats, and the Lesser Star of Africa, 317.4 carats, both of which are now part of the British Crown Jewels.

Armalcolite is a titanium-rich mineral with the chemical formula (Mg,Fe2+)Ti2O5. It was first found at Tranquility Base on the Moon in 1969 and is named for Armstrong, Aldrin and Collins, the three Apollo 11 astronauts. Together with tranquillityite and pyroxferroite, it is one of three new minerals that were discovered on the Moon.

Cassiterite is a tin oxide mineral. Its luster and multiple crystal faces produce a desirable gem. Cassiterite has been the chief tin ore throughout ancient history and remains the most important source of tin today.

Zircons from the Western Australian Jack Hills returned an age of 4.404 billion years, interpreted to be the age of crystallization, making them the oldest minerals so far dated on Earth.

The only color which sapphire cannot be is red – as red colored corundum is called ruby, another corundum variety. Pink colored corundum may be either classified as ruby or sapphire depending on locale.

An allotropy is a phenomenon of appearing, in the same state of aggregation, of all sorts varieties of the same chemical element, differing in physical properties and chemical. Coal is appearing mainly in the form of diamond, graphite, fullerene and graphene. Anthracite is simply a variety of the hard bituminous coal.