Opal and crystal do not typically grow together, as they form under different geological conditions. Opal is a mineraloid formed from silica gel that fills cavities or spaces in rocks, while crystals, like quartz, form from the gradual crystallization of minerals from molten rock or solutions. However, they can sometimes be found in the same geological environment, resulting in deposits where both may be present, but they do not grow interdependently or in conjunction.
Opal, being amorphous, is not really a mineral but a mineraloid. One of the scientifically accepted standards defining a mineral is that a mineral must have a crystal structure, which opal lacks. Many scientific groups and references, including the acclaimed Dana's System of Mineralogy, categorize Opal together with the "true" minerals. For this reason, Opal -- as well as other amorphous types that fall under the definition of a mineraloid.
Opal has an amorphous or non-crystalline structure, meaning it lacks a repeating atomic arrangement like that found in crystals. Instead, opal is made up of tiny silica spheres arranged in a disordered pattern, which gives it its beautiful color play known as "play-of-color."
Opal is not classified as a true crystal; instead, it is a mineraloid. Unlike crystals, which have a defined and ordered atomic structure, opal has a more irregular arrangement of silica spheres. This unique structure contributes to its characteristic play-of-color, making opal a popular gemstone despite its non-crystalline nature.
Some think it is in the quartz group.
diamond,saphire,opal,crystal,Amber,Amethyst ,ruby, jade and Crystal
The types of Opal that i am familiar with are White Opal, Fire Opal, Boulder Opal, Black Opal, Crystal Opal, Light Opal, Doublet Opal, Triplet Opal, Common Opal, Synthetic Opal, and Immitation Opal.
Crystal's grow by a process called nucleation.
The majority of minerals are crystalline materials.Examples: opal, halite, topaz.
Opal is known for its cleavage, which is the tendency of the stone to break along certain planes due to its crystal structure. This can give opal a characteristic pattern of fractures or cleavage surfaces when it is damaged or cut.
Opal is an amorphous mineral, which means it lacks a true crystal structure. It typically exhibits a smooth, glassy texture. Opal can also display a unique play-of-color caused by the diffraction of light, giving it a vibrant and iridescent appearance.
Opal is a hydrated, amorphous form of silica, ie sand. Silicon Dioxide, SiO2. Rather than a crystal formation, opal consists of tiny, tightly packed spheres of SiO2, with 3% to 20% of the mineral's weight as molecular water trapped amongst them.
There are 5 basic types of opal. These types are Peruvian Opal, Fire Opal, Girasol Opal, Common opal and Precious Opal.