quartz

===** Milky quartz ** ===   Milky quartz sample **Milk quartz** or **milky quartz** may be the most common variety of crystalline quartz and can be found almost anywhere. The white color may be caused by minute [|fluid inclusions] of gas, liquid, or both, trapped during the crystal formation. The cloudiness caused by the inclusions effectively bars its use in most optical and quality gemstone applications **__ Citrine __**__ is a variety of quartz whose color ranges from a pale yellow to brown. Natural citrines are rare; most commercial citrines are heat-treated [|amethysts] or [|smoky quartzes]. It is nearly impossible to tell cut citrine from yellow [|topaz] visibly, but they differ in hardness. Citrine has [|ferric] impurities, and is rarely found naturally. [|Brazil] is the leading producer of citrine, with much of its production coming from the state of [|Rio Grande do Sul]. The name is derived from [|Latin] citrina which means "yellow" and is also the origin of the word "citron." Sometimes citrine and amethyst can be found together in the same crystal, which is then referred to as ametrine....... __

__  The life cycle of the Sun __ The future of the planet is closely tied to that of the Sun. As a result of the steady accumulation of helium at the Sun's core, the [|star's total luminosity] will slowly increase. The luminosity of the Sun will grow by 10% over the next 1.1 [|Gyr] (1.1 billion years) and by 40% over the next 3.5 Gyr. Climate models indicate that the rise in radiation reaching the Earth is likely to have dire consequences, including the loss of the planet's oceans.