Milk opal without opalescence(dies 21-23 mm) Mexico, Hidalgo state

Price per piece of the smallest sample.
21 mm-length
23 - 5 mm thickness
The cost is from 7 to 350 rubles per piece (depends on the size, weight)

There are cute white translucent plates of soft-milky Mexican opal.
This is an ordinary opal without iridescent opalescence.
Opalescence in gemology is a physical phenomenon caused by optical inhomogeneity-usually it means ionization (associated with light interference), which is observed in "noble" opals, labradorite and other minerals, as well as in mother of pearl and pearls.

There are opals in nature, you don't even imagine......more than 450 varieties.
Details will not go down and list, but from this numbers, only a small part of it belongs to the noble Opala ( those who have rainbow light), then... there's a dozen that give solid opal opalescence is a white and fiery polupronicaema and translucent).
The rest, and there are more than a hundred types of opals, are completely opaque or slightly translucent and have no effect.

In fact, opal is hydrated amorphous form of silica its water content may range from 140 to 3% by weight but is usually between 21 to 6%.
Because of its amorphous character it is classified as mineraloid, in contrast to crystalline forms of silica which are classed as minerals.
It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, most commonly found with limonite, Sandstone, rhyolite, marl and basalt .

The main distinctive common property opals, oily luster conchoidal cleavage.
However, dry and dehydrated opals can give dim skol.

And finally..opal is a stone of spiritual and mental, not material goods.
Well suited to creative individuals.
Also the story goes that in Ancient Rome, the opal was considered a symbol of love and passed this legend and belief still...