<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>000110 - Disclosure - 6. Due On Mineral Rights Acquisitions</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><CurrencyCode /><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName /><CurrencySymbol /><contextRef><ContextID>D130101_130630</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0001475430</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2013-01-01T00:00:00</PeriodStartDate><PeriodEndDate>2013-06-30T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="6 Months Ended" /><Label Key="Calendar" Id="1" Label="Jun. 30, 2013" /></Labels></Column></Columns><Rows><Row FlagID="0"><Id>1</Id><IsAbstractGroupTitle>true</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>1</Level><ElementName>us-gaap_DisclosureTextBlockAbstract</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Notes</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_DeferredPolicyAcquisitionCostsTextBlock1</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="D130101_130630" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;!--egx--&gt;&lt;p style='margin:0in;margin-bottom:.0001pt;margin-top:0in;margin-right:53.5pt;margin-bottom:0in;margin-left:37.9pt;margin-bottom:.0001pt;text-align:justify;text-indent:-.25in'&gt;&lt;b&gt;6.&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp; &lt;/b&gt;&lt;b&gt;Due On Mineral Rights Acquisitions&lt;/b&gt;&lt;/p&gt; &lt;p style='margin:0in;margin-bottom:.0001pt'&gt;&amp;nbsp;&lt;/p&gt; &lt;p style='margin:0in;margin-bottom:.0001pt;margin-left:.5in;text-align:justify'&gt;The Company is required to make certain payments in respect of its 2011 acquisition of the Garrett Property and its 2012 acquisitions of the Elijah Property and the Kenty Property and its 2013 acquisitions of the Mortimer Property, the Coppell Property, and the Cree Property. These payments are due to Firelake Resources Inc., Shining Tree Resources Corp., Brian McClay, Red Pine Exploration Inc., Shelly Moretti, Jacques Robert and Michael Tremblay (collectively), respectively, and Midnight Capital Corp.; the companies and individuals from which the properties were acquired. The amounts due are unsecured, non-interest bearing, and are due as follows:&lt;/p&gt; &lt;p style='margin:0in;margin-bottom:.0001pt;margin-top:0in;margin-right:.2pt;margin-bottom:0in;margin-left:.5in;margin-bottom:.0001pt;text-align:justify'&gt;&amp;nbsp;&lt;/p&gt; &lt;table border="0" cellspacing="0" cellpadding="0" style='margin-left:.7in;border-collapse:collapse'&gt; &lt;tr align="left"&gt; &lt;td width="127" valign="top" style='width:95.4pt;border:none;border-top:solid windowtext 1.5pt;padding:0in 5.4pt 0in 5.4pt'&gt; &lt;p style='margin:0in;margin-bottom:.0001pt'&gt;2013 (six months) &lt;/p&gt; &lt;/td&gt; &lt;td width="125" valign="top" style='width:1.3in;border:none;border-top:solid windowtext 1.5pt;padding:0in 5.4pt 0in 5.4pt'&gt; &lt;p style='margin:0in;margin-bottom:.0001pt'&gt;$&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; 766,000&lt;/p&gt; &lt;/td&gt; &lt;/tr&gt; &lt;tr align="left"&gt; &lt;td width="127" valign="top" style='width:95.4pt;padding:0in 5.4pt 0in 5.4pt'&gt; &lt;p style='margin:0in;margin-bottom:.0001pt'&gt;2014&lt;/p&gt; &lt;/td&gt; &lt;td width="125" valign="top" style='width:1.3in;padding:0in 5.4pt 0in 5.4pt'&gt; &lt;p style='margin:0in;margin-bottom:.0001pt'&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; 650,000&lt;/p&gt; &lt;/td&gt; &lt;/tr&gt; &lt;tr align="left"&gt; &lt;td width="127" valign="top" style='width:95.4pt;border:none;border-bottom:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt'&gt; &lt;p style='margin:0in;margin-bottom:.0001pt'&gt;2015&lt;/p&gt; &lt;/td&gt; &lt;td width="125" valign="top" style='width:1.3in;border:none;border-bottom:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt'&gt; &lt;p style='margin:0in;margin-bottom:.0001pt'&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; 300,000&lt;/p&gt; &lt;/td&gt; &lt;/tr&gt; &lt;tr align="left"&gt; &lt;td width="127" valign="top" style='width:95.4pt;border:none;border-bottom:solid windowtext 1.5pt;padding:0in 5.4pt 0in 5.4pt'&gt; &lt;p style='margin:0in;margin-bottom:.0001pt'&gt;&lt;b&gt;Total&lt;/b&gt;&lt;/p&gt; &lt;/td&gt; &lt;td width="125" valign="top" style='width:1.3in;border:none;border-bottom:solid windowtext 1.5pt;padding:0in 5.4pt 0in 5.4pt'&gt; &lt;p style='margin:0in;margin-bottom:.0001pt'&gt;&lt;b&gt;$&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; 1,716,000&lt;/b&gt;&lt;/p&gt; &lt;/td&gt; &lt;/tr&gt; &lt;/table&gt; &lt;p style='margin:0in;margin-bottom:.0001pt'&gt;&amp;nbsp;&lt;/p&gt; &lt;p style='margin:0in;margin-bottom:.0001pt;margin-top:0in;margin-right:.2pt;margin-bottom:0in;margin-left:.5in;margin-bottom:.0001pt;text-align:justify'&gt;As of June 30, 2013, the Company is in arrears on its payments by $184,000. This amount has been included above in the installments due for 2013.&lt;/p&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>The entire disclosure for deferred policy acquisition costs.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 944

 -SubTopic 30

 -Section 50

 -Paragraph 1

 -URI http://asc.fasb.org/extlink&amp;oid=6967983&amp;loc=d3e11264-158415



Reference 2: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 944

 -SubTopic 30

 -Section 50

 -Paragraph 4

 -URI http://asc.fasb.org/extlink&amp;oid=6481813&amp;loc=d3e11407-158417



</ElementReferences><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>6. Due On Mineral Rights Acquisitions</Label></Row></Rows><Footnotes /><IsEquityReport>false</IsEquityReport><ReportName>6. Due On Mineral Rights Acquisitions</ReportName><MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel><SharesRoundingLevel>UnKnown</SharesRoundingLevel><PerShareRoundingLevel>UnKnown</PerShareRoundingLevel><ExchangeRateRoundingLevel>UnKnown</ExchangeRateRoundingLevel><HasCustomUnits>true</HasCustomUnits><IsEmbedReport>false</IsEmbedReport><IsMultiCurrency>false</IsMultiCurrency><ReportType>Sheet</ReportType><RoleURI>http://www.joshuagoldresources.com/20130630/role/idr_Disclosure6DueOnMineralRightsAcquisitions</RoleURI><NumberOfCols>1</NumberOfCols><NumberOfRows>2</NumberOfRows></InstanceReport>
