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[Bluesky2000]

The crystal is transparent quartz crystalloid. To know about the crystal, we need to learn about the mineral of quartz first. Quartz is one of the minerals that distributes widely in the earth’s crust. Its chemical property is silica and the chemical formula is SiO2. The quartz has a large family, which can be divided into three categories: phanerocrystalline, cryptocrystalline and amorphous. The crystal belongs to the category of phanerocrystalline, which means the transparent quartz crystalloid.

The crystal is usually colorless and transparent, but when it contains the impurities of some other metal element (pigment ion), it takes on purple, golden yellow, brown or black and few of them pink. After research, the purple crystal (amethyst) takes on purple mainly because it contains Mn and Fe3+; the pink one is the effect of Mn, Ti ion and hydroxide; the golden yellow one is because of the Fe2+; Some colors are caused by the inclusion impurities of the crystal.

The crystal takes on glass luster, the refractive index is 1.544 – 1.553, the birefringence is 0.009 and the dispersion is 0.013. The amethyst and tawny crystal have polychroism.

The shape of the crystal appears hexagonal, there are usually bands on the cylindrical surface and they can be produced in vug with charming design. There is no cleavage and the fracture is conchoidal. The Mohs hardness is 7, the relative density is 2.56 – 2.66 and it has piezoelectricity. The crystal often contains gas and liquid inclusion. Sometimes there are needlelike mineral (rutile, apyrite, actinolite etc.) inclusions, also with the shining hematite and mica sheet.

The crystal is mainly produced in the geode of pegmatite and quartz vein. The famous crystal origins in the world are Brazil and Madagascar and so on.

The amethyst is the outstanding one amount the numerous crystal members and one of the most valuable one in the quartz family. The ancients think that amethyst can enhance mutual understanding; earn money when doing business; protect the soldiers to win; help the hunters to resist infectious disease and restrain the evil thought. The amethyst is the birthstone of February. yoNEED Jewelry

[JuliaY]

Crystal!!! Big faceted crystal stone rings or pendants sparkle brilliantly; or, gorgeous crystal pave deco jewelry, be-dazzled for Bling-Bling statements; pure clear crystals, understated black jet crystals, glaming garnet crystals, and graceful amethyst crystals etc.!! - JewelrySaga

[Bluesky2000]

I agree with you. The crystal is very beautiful. I'm sure that most people will like them - yoNEED Jewelry

[Jewelry]

Something is crystalline if the atoms or ions that compose it are arranged in a regular way (i.e, a crystal has internal order due to the periodic arrangement of atoms in three dimensions). Gems are described as amorphous if they are non-crystalline.
Crystals characterized by well developed crystal faces (external surfaces) are described as euhedral . Crystals do not always show well developed crystal faces seen on euhedral examples. A crystal is built up by arranging atoms and groups of atoms in regular patterns, for example at the corners of a cube or rectangular prism. The basic arrangement of atoms that describes the crystal structure is identified. This is termed the unit cell. Crystals must be charge balanced. This means that the amount of negative charge must be compensated by the same amount of positive charge.

[mikebush]

crystal is a hard material...