SLATE	A very fine grained metamorphic rock derived from sedimentary rock shale. Characterized by an excellent parallel cleavage entirely independent of original bedding, by which cleavage the rock may be split easily into relatively thin slabs.
GROUP	Metamorphic
COMMON ROCK-FORMING MINERAL GROUP	Siliceous
COMPOSITION	Muscovite, chlorite, kaolinite, micas, quartz and other accessory minerals.
HARDNESS	Soft to as Hard and dense as granite.
MOHS' SCALE	2.5 - 5.5
POROSITY	0.4 - 5.0 %
ABSORPTION	0.1 - 1.7 %
WEATHERING CHARACTERISTICS	Due to the wide ranges of slate, this stone has wide ranges of weathering. Cleft planes provides permeability for water penetration resulting in spalling and flaking. Slates that have a high kaolinite content (a clay) display accelerated rate of deterioration in wet environments.
TENDENCIES	Absorbs oils and liquids and get scratches easily.
COLOURS	Colours vary widely.
NOTATIONS	Sealing to minimize staining... Coloured slates benefit from colour enhancing treatments designed to magnify and protect the natural colours. When dealing with coloured slates there are two distinct types, Fading and Unfading. After a period of exposure to the environment (sun/water) fading slates will alter generally to a lighter colour. The unfading varieties will retain their true colours. Multi-coloured slates used for flooring will undergo colour changes in abrasive foot-traffic areas. The colours in these varieties of slates are in thin bedded layers... Some slates will dust for a while after installation on floors as loose scale is removed by foot traffic. This will stop as the surface settles in, usually in a few weeks. The majority of the multi-coloured slates are what are termed "clay slates" and generally have a high content of clay minerals and are geologically classed as a low-ranked slates, those in which the metamorphic process was halted at a very early stage. These slates weather poorly in exterior wet/humid climates.