The plagioclase crystals vary greatly in size, some being mere microliths while others are over the eighth of an inch in length.
Monoclinic felspar does, however, occur in some of these rocks; but the difficulty of ascertaining the precise character of microliths renders it unsafe to speculate on the amount of sanidine which may be present.
Crystals of leucite with microliths and cavities darkened by magnetite dust; also, containing crystals of magnetite.
Under the next microscope you can see the microliths much more distinctly (Fig.
The dark bands are lines of microliths formed as the lava cooled.
A slice of volcanic glass showing the lines of crystallites and microliths which are the beginnings of crystals.
For this lava, covered by the crust above, has remained very hot for a long time, and the crystals have had time to build themselves up out of the microliths and crystallites.
Many of these so-called arrow-heads may have been nothing more than microliths used for a great variety of purposes.
In 1909 Breuil and Obermaier found in the grotto of Valle, in northern Spain, a classic Azilian deposit, forming the lower levels of a series rich in these microliths or pygmy flints.
In Portugal the hearths of Mugem and Cabeco da Arruda are distinguished by their triangular microliths and are undoubtedly Pre-Neolithic, because there is neither pottery nor any trace of domesticated animals, excepting, possibly, the dog.
We know that similar microliths were used as arrow points in predynastic Egypt.
This rock displays a few small phenocrysts of oligoclase and pyroxenes in a blurred glassy groundmass exhibiting the felspar and pyroxene microliths in process of development (sp.
It differs in some respects from the prevailing rock, since it displays prismatic augite as well as felspar microliths in its glassy groundmass, and is for this reason referred to genus 20 of the augite-andesites.
They have a crypto-crystalline groundmass where the felsitic structure is in process of development and where the pyroxene prisms or microliths are very minute.
In the vitreous shell the felspar microliths are much less developed both in size and number than in the central portion of the bomb.
At times there can be recognised a later generation of minute felspar microliths between the much larger lathes.
It displays microporphyritic plagioclase in a ground-mass formed mainly of a smoky, almost isotropic glass, in which numbers of felspar microliths (ยท1 mm.
Spherulites may be regarded as radiate aggregates of such microliths (mostly felspar mixed with quartz or tridymite).
The larger microliths may contain enclosures of glass, and it is very common to find that the prisms have hollow, funnel-shaped ends, which are filled with vitreous material.
In other cases the crystalline arrangement of the microlithsis less perfect, and branching, arborescent or feathery groupings are produced (e.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "microliths" in a variety of sentences. We hope that you will now be able to make sentences using this word.
