https://wserv3.esc.cam.ac.uk/p1acollections/items/browse?page=20&sort_field=Dublin+Core%2CTitle&output=atom <![CDATA[1A Collections]]> 2024-04-09T21:24:52+01:00 Omeka https://wserv3.esc.cam.ac.uk/p1acollections/items/show/211 <![CDATA[<h2>Interstitial</h2>]]> Have a look at the granodiorite (L120) in the 1A Reference Series.]]> 2019-07-04T09:53:10+01:00

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.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/212 <![CDATA[<h2>Intrusive</h2>]]> Compare with extrusive.]]> 2019-07-04T09:53:10+01:00

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.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/213 <![CDATA[<h2>Isotropic</h2>]]> Compare with anisotropic.]]> 2019-07-04T09:53:11+01:00

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.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/214 <![CDATA[<h2>Kinks</h2>]]> 2019-07-04T09:53:11+01:00

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.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/169 <![CDATA[<h2>Lamellar twinning</h2>]]> 2019-07-04T09:52:57+01:00

Title

Lamellar twinning

Subject

Many parallel twins can be produced within one mineral grain by multiple parallel twin planes. This is known as lamellar twinning. It is a diagnostic characteristic of plagioclase feldspar, and is sometimes referred to as albite twinning.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/215 <![CDATA[<h2>Lath</h2>]]> 2019-07-04T09:53:12+01:00

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.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/216 <![CDATA[<h2>Length fast</h2>]]> Compare with length slow.]]> 2019-07-04T09:53:12+01:00

Title

Length fast

Subject

All anisotropic minerals have fast and slow vibration directions. If the fast vibration direction is parallel to the direction of elongation of the crystal, the crystal is length fast.

Description

Compare with length slow.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/217 <![CDATA[<h2>Length slow</h2>]]> Compare with length fast.]]> 2019-07-04T09:53:12+01:00

Title

Length slow

Subject

All anisotropic minerals have fast and slow vibration directions. If the slow vibration direction is parallel to the direction of elongation of the crystal, it is said to be length slow.

Description

Compare with length fast.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/218 <![CDATA[<h2>Leucocratic</h2>]]> 2019-07-04T09:53:13+01:00

Title

Leucocratic

Subject

Leucocratic rocks have a low colour index. That is to say that <30 vol% of the rock is made up of ferromagnesian minerals.

]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/219 <![CDATA[<h2>Lineation</h2>]]> 2019-07-04T09:53:13+01:00

Title

Lineation

Subject

This refers to any pervasive linear feature in a rock. It can be produced by the intersection of two foliations (planar rock fabrics) or by the alignment of linear objects such as elongate grains in the rock. Linear fabrics can be primary (e.g. flow lineations) or secondary (e.g. mineral alignment during metamorphism).

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