<![CDATA[1A Collections]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/browse?page=21&sort_field=added&output=rss2 Tue, 09 Apr 2024 21:25:16 +0100 p1acollections@esc.cam.ac.uk (1A Collections) Zend_Feed http://blogs.law.harvard.edu/tech/rss <![CDATA[Habit (or form)]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/206

Title

Habit (or form)

Subject

The three dimensional shape of a crystal. The crystal structure of a mineral influences the characteristic habit(s) which it displays. For example, biotite mica tends to display a platy or tabular habit because its crystal lattice is made up of sheets.
]]> Fri, 21 Jun 2019 16:07:39 +0100 <![CDATA[Hardness]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/207

Title

Hardness

Subject

Hardness is measured on the Mohs scale. A hard mineral is rigid, resistant to pressure and is not easily scratched. Determining the hardness (or relative hardness) of a mineral in hand specimen can aid your identification of the mineral.
]]> Fri, 21 Jun 2019 16:08:47 +0100 <![CDATA[Hypabyssal]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/208

Title

Hypabyssal

Subject

Hypabyssal rocks and textures are those associated with very shallow magmatic intrusions, where cooling is moderately rapid. This term is restricted to relatively small intrusive bodies centimetres to tens of metres in diameter.
]]> Fri, 21 Jun 2019 16:09:13 +0100 <![CDATA[Hypermelanic]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/209

Title

Hypermelanic

Subject

Hypermelanic rocks have a very high colour index. That is to say that >90 vol% of the rock is made up of ferromagnesian minerals.
]]> Fri, 21 Jun 2019 16:10:50 +0100 <![CDATA[Inclusion]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/210

Title

Inclusion

Subject

As a crystal grows in a magma, tiny blobs of melt can become trapped in its structure. These are melt inclusions. Small crystals of other minerals can also become trapped. These are mineral inclusions.

Description

Have a look at the alkali basalt (L100), the porphyritic rhyolite (L110) and the garnet schist (L504) in the 1A Reference Series.
]]> Fri, 21 Jun 2019 16:13:23 +0100 <![CDATA[Interstitial]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/211

Title

Interstitial

Subject

An igneous texture in which large anhedral grains fill the gaps between earlier crystallising phases.

Description

Have a look at the granodiorite (L120) in the 1A Reference Series.
]]> Fri, 21 Jun 2019 16:15:37 +0100 <![CDATA[Intrusive]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/212

Title

Intrusive

Subject

Rocks which have formed by the intrusion of igneous material below the surface of the Earth are described as intrusive.

Description

Compare with extrusive.
]]> Fri, 21 Jun 2019 16:16:41 +0100 <![CDATA[Isotropic]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/213

Title

Isotropic

Subject

The speed of light through any medium is inversely proportional to the refractive index of the medium. The refractive index of a mineral is determined by the arrangement and type of atoms within its structure.

If the structure of the mineral allows light to travel at the same velocity through the mineral in all orientations, the mineral is isotropic. That is to say, it has the same refractive index in all directions. Under cross-polarised light isotropic minerals always appear black. Garnet is an isotropic mineral

Description

Compare with anisotropic.
]]> Fri, 21 Jun 2019 16:18:32 +0100 <![CDATA[Kinks]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/214

Title

Kinks

Subject

These are bands of deformation in which the orientation is changed due to slipping on several parallel slip planes. Kinks can occur in a single crystal or in foliated rock.
]]> Fri, 21 Jun 2019 16:19:38 +0100 <![CDATA[Lath]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/215

Title

Lath

Subject

A crystal with an elongate, needle-like form is said to be lath-shaped. This term is most commonly applied to elongate crystals of feldspar in igneous rocks.
]]> Fri, 21 Jun 2019 16:20:25 +0100